LGPL 2.1 + GPL 3 = problems?

[Jesse Hannah]

I'm going to go over both licenses again myself, but I'd like to hear  
others' opinions about this; I'm not as well-versed in the LGPL as I  
am the GPL, and I'm not as well-versed in either of them as I should  
be, but I digress.

Would using (linking, including/redistributing unmodified) a library  
that's licensed under the LGPL version 2.1 with a program that's  
licensed under the GPL version 3 cause any weird problems? My initial  
guess is that just linking the libraries, or redistributing the  
source code unmodified---either entirely separate from, or something  
like in its own folder in the same package with the GPL'd code---
would be fine, but any copy-and-paste inclusion, modification and  
attribution might raise some eyebrows and/or compatibility issues  
(like I said, I'll be reading the fine print one more time to see if  
I can spot anything).

Sorry if this question's been asked before, and I know that the (L)
GPL 3 is still being looked over by the OSI. This is probably a  
question that would be asked at some time or another, probably  
repeatedly, since there almost certainly will be programs that will  
be (L)GPL 3-licensed, that will want to link to, redistribute, or use  
code from libraries that will still be LGPL 2.1-licensed. It's best  
this gets brought up early in the life of the GPL 3 so that if there  
are any big compatibility issues, people will know early on.

Anyone's thoughts, analysis, feedback, telling me to GTFO (well,  
okay...maybe not that last bit) are all appreciated. I'm new here, so  
be nice. :)

--jbh

~~~~
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        <jesse.hannah@...>
        <jesse.hannah@...>

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[Arnoud Engelfriet-2]

Jesse Hannah wrote:
> Would using (linking, including/redistributing unmodified) a library  
> that's licensed under the LGPL version 2.1 with a program that's  
> licensed under the GPL version 3 cause any weird problems? My initial  

My initial thought is that you can't do that, or at least you can't
distribute the result.

GPLv3 defines any linked libraries as being part of the
Corresponding Source, assuming the GPLv3 program "is specifically
designed to require" this LGPLv21 library.

Article 5c of GPLv3 says that "You must license the entire work,
as a whole, under this License to anyone who comes into possession
of a copy."

The problem is that you can't license the LGPLv21 parts under
GPLv3.

LGPLv21 has an automatic compatibility provision with GPLv2,
so in the past this was never a problem.

Arnoud

--
Arnoud Engelfriet, Dutch & European patent attorney - Speaking only for myself
Patents, copyright and IPR explained for techies: http://www.iusmentis.com/
              Arnoud blogt nu ook: http://blog.iusmentis.com/

[Jesse Hannah]

On 15 Jul 2007, at 01:59, Arnoud Engelfriet wrote:
> Article 5c of GPLv3 says that "You must license the entire work,
> as a whole, under this License to anyone who comes into possession
> of a copy."
>
> The problem is that you can't license the LGPLv21 parts under
> GPLv3.
>
> LGPLv21 has an automatic compatibility provision with GPLv2,
> so in the past this was never a problem.

But I could license the LGPL v2.1 parts under the LGPL v3:

     This library is free software; you can redistribute it and/or
     modify it under the terms of the GNU Lesser General Public
     License as published by the Free Software Foundation; either
     version 2.1 of the License, ***or (at your option) any later  
version.***

The way I'm reading that, I'm free to redistribute the library under  
the LGPL v3 if I want to, meaning (presumably) that I can use it with  
a GPLv3 program. Does that sound right?

--jbh

~~~~
Jesse B Hannah
        <jesse.hannah@...>
        <jesse.hannah@...>

Homepage: <http://www.lifeisleet.com>
Weblog: <http://blog.lifeisleet.com>
IRC Handle: <jbhannah@...>

GPG Key: 0xA6DC3EF3
        Available from the keyservers or at
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[Philippe Verdy]

Arnoud Engelfriet wrote:

> Jesse Hannah wrote:
> > Would using (linking, including/redistributing unmodified) a library
> > that's licensed under the LGPL version 2.1 with a program that's
> > licensed under the GPL version 3 cause any weird problems? My initial
>
> My initial thought is that you can't do that, or at least you can't
> distribute the result.
>
> GPLv3 defines any linked libraries as being part of the
> Corresponding Source, assuming the GPLv3 program "is specifically
> designed to require" this LGPLv21 library.
>
> Article 5c of GPLv3 says that "You must license the entire work,
> as a whole, under this License to anyone who comes into possession
> of a copy."
>
> The problem is that you can't license the LGPLv21 parts under
> GPLv3.
>
> LGPLv21 has an automatic compatibility provision with GPLv2,
> so in the past this was never a problem.

You can do that if the library was licensed explicitly under LGPL 2 "or
later", meaning that it can be distributed under the terms of LGPL v3.
The GPLv3 contains the wordings necessary that explicitly says that linking
it with LGPLv3 is creating a combined work that is covered by GPLv3 as
whole, but whose individual components remain under their respective
licences.

In other words, the library used in your GPLv3-licensed product will remain
licensed now under LGPL v3 by its original author(s), as allowed by the
LGPLv2 licence from that(these) author(s)...

[Philippe Verdy]

Note: the situation is exactly similar with the case where you want to
combine several works licenced with different versions of the GPL:
==> You can distribute your new combined work only under the terms of the
highest version of the individual licences of the GPL-covered components,
provided that they are ALL licenced with a copyright notice that explicitly
states that they allow this new higher version.

For this reason, it is highly recommended, for any programs you want to
publish under the GPL to use the terms "version x or any later version as
published by the Free Software Foundation" within your licencing terms.

If your copyright notice that references the appropriate licence to use only
specifies a precise version of the licence, you can still use a higher
version according to the terms of this referenced original licence. However,
if you really want to exclude any higher version, your copyright notice
should explicitly contain an "additional restriction" (as defined and
allowed in the GPL licences), such as:

        <one line for the name of the program and describing what it does>
        Copyright (C) <year> <author name>
        This library is a free software; you may redistribute it or modify
it
        according to the terms of the "GNU Lesser General Public License"
        version 2.1 as published by the Free Software Foundation, with the
        additional restriction that any later versions are excluded.

Without this EXPLICIT additional restriction in your copyright notice, the
original terms of the GPL v2.1 license allows upgrading the version of the
referenced license. Almost all GPL- or LGPL-licensed works do not have such
explicit "additional restriction", and can then be used or conveyed under
the terms of a newer version.

Reread for example the section 4 of the GPLv3 which explicitly states that
authors can decide which version of the GPL they accept. The "or any later
version" is an explicit statement that is now highly recommended, but this
is not the only option. GPLv3 allows later versions to be acceptable only
through acceptation by a given proxy. And it also allows an author to
enumerate the accepted version numbers.

These are viewed as additional permissions or restrictions, according to
section 7, which also allows changing the terms for the limitation of
warranty, or allows requiring or prohibiting the preservation of the
original author names, or limiting the usage of their personal names within
commercial products:

For example in trademarks where an author like "Linus Torvald" could
restrict the use of his name within the trademark of a commercial
distribution of a Linux Kernel, thus saying that the licence does not cover
the right to use this name in a trademark like "Torvald Linux (tm)" or in
ads like "Buy the unbreakable XYZ Linux now, featuring the new kernel
version x.y made by Linux Torvald" (in the countries where it would be legal
without permission unless the name was reserved, i.e. not in France at least
where French authors are also protected by their exclusive moral right
recognized by the Civil Law, so that French authors do not need to make such
explicit statement about the usage of their name, or photo, as this
exclusive protection by the French law on Authors Rights, now part of the
"DADVSI" Act, is extended internationally by WIPO in its binding treaties or
conventions).

Philippe

[Arnoud Engelfriet-2]

Jesse Hannah wrote:
> But I could license the LGPL v2.1 parts under the LGPL v3:
>
>     This library is free software; you can redistribute it and/or
>     modify it under the terms of the GNU Lesser General Public
>     License as published by the Free Software Foundation; either
>     version 2.1 of the License, ***or (at your option) any later  
> version.***

If the library says that, then yes. But not all LGPL libraries carry
that particular message.

> The way I'm reading that, I'm free to redistribute the library under  
> the LGPL v3 if I want to, meaning (presumably) that I can use it with  
> a GPLv3 program. Does that sound right?

Yes, because the LGPLv3 allows conversion of the license to GPLv3.
With that conversion you can comply with GPLv3 for the entire work.

Arnoud

--
Arnoud Engelfriet, Dutch & European patent attorney - Speaking only for myself
Patents, copyright and IPR explained for techies: http://www.iusmentis.com/
              Arnoud blogt nu ook: http://blog.iusmentis.com/

[Philippe Verdy]

Arnoud Engelfriet wrote:

> Jesse Hannah wrote:
> > But I could license the LGPL v2.1 parts under the LGPL v3:
> >
> >     This library is free software; you can redistribute it and/or
> >     modify it under the terms of the GNU Lesser General Public
> >     License as published by the Free Software Foundation; either
> >     version 2.1 of the License, ***or (at your option) any later
> > version.***
>
> If the library says that, then yes. But not all LGPL libraries carry
> that particular message.

True.

> > The way I'm reading that, I'm free to redistribute the library under
> > the LGPL v3 if I want to, meaning (presumably) that I can use it with
> > a GPLv3 program. Does that sound right?
>
> Yes, because the LGPLv3 allows conversion of the license to GPLv3.
> With that conversion you can comply with GPLv3 for the entire work.

Wrong ! The LGPGL does NOT authorize the conversion of the licences covering
other necessary components. The terms that allows such promotion are those
found in the licences of those components.

What the LGPL says is that your modified library as a whole, licenced under
LGPL v3 can be also licenced under GPLv3 only (excluding any later version
of the GPL), and in that case, the promotion of LGPL to GPL makes an
explicit "additional restriction" to the default terms of the GPLv3 which
normally allows by default "version 3.0 of the GPL or any later version".

This explicit restriction found in the LGPL v2.1 or in LGPL v3 only applies
to the library as a whole, not to the individual parts of it that may be
covered individually by other licences (such as a prior version of the LGPL
or public domain).

[Arnoud Engelfriet-2]

Philippe Verdy wrote:
> Arnoud Engelfriet wrote:
> > Yes, because the LGPLv3 allows conversion of the license to GPLv3.
> > With that conversion you can comply with GPLv3 for the entire work.
>
> Wrong ! The LGPGL does NOT authorize the conversion of the licences covering
> other necessary components. The terms that allows such promotion are those
> found in the licences of those components.

What I meant is that you can apply the terms of the GPL to any
LGPL work instead of the LGPL terms. See LGPL 2 section 3, first sentence.

I did make a mistake in assuming that this provision was also present
in LGPL 3. It is not. LGPL 3 simply says that you can convey the software
"under the GNU GPL, with none of the additional permissions of this License
applicable to that copy." (LGPLv3 section 2b).

Arnoud

--
Arnoud Engelfriet, Dutch & European patent attorney - Speaking only for myself
Patents, copyright and IPR explained for techies: http://www.iusmentis.com/
              Arnoud blogt nu ook: http://blog.iusmentis.com/

[Philippe Verdy]

> -----Message d'origine-----
> De : Arnoud Engelfriet [mailto:arnoud@...]
> Envoyé : dimanche 15 juillet 2007 13:04
> À : Philippe Verdy
> Cc : license-discuss@...
> Objet : Re: LGPL 2.1 + GPL 3 = problems?
>
> Philippe Verdy wrote:
> > Arnoud Engelfriet wrote:
> > > Yes, because the LGPLv3 allows conversion of the license to GPLv3.
> > > With that conversion you can comply with GPLv3 for the entire work.
> >
> > Wrong ! The LGPGL does NOT authorize the conversion of the licences
> covering
> > other necessary components. The terms that allows such promotion are
> those
> > found in the licences of those components.
>
> What I meant is that you can apply the terms of the GPL to any
> LGPL work instead of the LGPL terms. See LGPL 2 section 3, first sentence.

Wrong! Not any version of the GPL, unless otherwise specified in an
additional permission in the copyright notice of your library, or specified
explicitly in a later version of the ***LGPL*** (***and*** your library
specifies that it can be used according to a later version of the LGPL,
something that most LGPL libraries specify in their copyright notice).

For now this is not a problem because LGPLv3 explicitly allows using GPLv3,
so that a library originally licenced under LGPLv2.1 "or any later version"
can be used in a LGPLv3 library that can still used in a GPLv3 program, only
because the LGPLv2.1 permits using the terms of LGPLv3 that contains the
"additional permission" to the GPLv2...

But if the FSF publishes a GPLv3.1 update but no update to LGPLv3.0 to
authorize GPLv3.1, then you won't be able to use the LGLv3.0 library in a
GPLv3.1 program without either:

(1) Asking to the original author of the LGPLv3 library this additional
permission to convey your modified library using GPLv3.1 with an explicit
additional permission in your copyright notice like:

        "This library is free software: you can redistribute it and/or
        modify it under the terms of the GNU Lesser General Public License
        (LGPL) as published by the Free Software Foundation (FSF), either
        Version 3 of the License, or (at your option) any later version, or
        at your option) you may also use the terms of the GNU General Public
        License (GPL) version 3.1, as published by the FSF, or any later
        version of the GPL"
       
The last part "or any later version of the GPL" is optional, but may be used
only if the author has authorized it.

(2) Waiting for the FSF to publish a later version of the LGPL that allows
using the library within a GPL v3.1 program. Note that "or any later version
of the GPL" may be present absent from the updated LGPL v3.1, and if so, you
won't be able to include it in the copyright notice of your program without
asking for permission to the original author of the LGPL v3 library!

As both GPL v3.0 and LGPL v3.0 were published, this does not make any
problem for now. But it may happen with possible future versions of the
GPLv3, or with programs licenced by their original authors under GPLv3.0
with additional restrictions such as those excluding later versions of the
GPL.

For now, all libraries licenced under LGPLv2.1 or LGPLv3.0 are compatible
with each other and with GPL 3.0 and GPL 3.1 programs, provided that GPL 3.0
programs and LGPL 3.0 libraries include the "any later version" statement in
their copyright notice, and you licence your combined works using at least
the highest version number of these component licences

You CANNOT distribute your combined work under the GPL v2.1 or LGPLv2.1 if
only one component is licenced under GPL v3.0 or LGPL v3, and this means
that the new section about the required extension of Patent Licencing in GPL
v3.0 will apply to your combined work.

Philippe.

[Philippe Verdy]

De : Arnoud Engelfriet [mailto:arnoud@...] :
> What I meant is that you can apply the terms of the GPL to any
> LGPL work instead of the LGPL terms. See LGPL 2 section 3, first
> sentence.

Note the exact statement is:
        "(If a newer version than version 2 of the ordinary GNU General
        Public License has appeared, then you can specify that version
        instead if you wish.)"

But it is not cleared enough to explicitly state which "newer version" of
the GPL is usable, notably because it does not explicitly say if it is
valid. What makes the statement clear is "as published by the Free Software
Foundation" in the copyright notice.

These contestable terms (because it could include any other licence
compatible with the GPLv2, including one containing some terms not published
by the FSF itself) were revised in GPLv3 (section 14) and LGPLv3, by
explaining where such extended permission can be found:

        "If the Program specifies that a certain numbered version of the
        GNU General Public License “or any later version” applies to it,
        you have the option of following the terms and conditions either
        of that numbered version or of any later version published by the
        Free Software Foundation. If the Program does not specify a
        version number of the GNU General Public License, you may choose
        any version ever published by the Free Software Foundation."

This statement explicitly makes additional restrictions to the future
versions of the GPL (in the sense of section 10 of the GPLv3), as explained
in the following paragraphs in that section 14 of the GPLv3.

This interpretation was confirmed by the FSF, and justified the need to
include an upgrade to the referenced version of the GPL, to be fair with
what was done with the LGPLv2 in the past (when used in combination with
other non-FSF but compatible licenses).

Philippe

[Arnoud Engelfriet-2]

Philippe Verdy wrote:
> > What I meant is that you can apply the terms of the GPL to any
> > LGPL work instead of the LGPL terms. See LGPL 2 section 3, first sentence.
>
> Wrong! Not any version of the GPL, unless otherwise specified in an
> additional permission in the copyright notice of your library, or specified
> explicitly in a later version of the ***LGPL*** (***and*** your library

I did not say "any version of the GPL".

"You may opt to apply the terms of the ordinary GNU General Public
License instead of this License to a given copy of the Library."

This is verbatim from LGPL version 2.1, section 3, first sentence.
I fail to see what this has to do with additional permissions.

Arnoud

--
Arnoud Engelfriet, Dutch & European patent attorney - Speaking only for myself
Patents, copyright and IPR explained for techies: http://www.iusmentis.com/
              Arnoud blogt nu ook: http://blog.iusmentis.com/

[John Cowan]

Jesse Hannah scripsit:

> Would using (linking, including/redistributing unmodified) a library
> that's licensed under the LGPL version 2.1 with a program that's
> licensed under the GPL version 3 cause any weird problems?

No, it would not.

> My initial guess is that just linking the libraries, or redistributing
> the source code unmodified---either entirely separate from, or something
> like in its own folder in the same package with the GPL'd code---
> would be fine,

Quite right -- not because of the special features of the LGPL that
allow conversion to the GPL, but because the whole point of the LGPL
is that an LGPLed library can be combined into a larger work that
uses the library, and this larger work may have any desired license
consistent with the licenses of its non-LGPL components,
even a proprietary one.

For example, one may combine an LGPLed library with a BSD-licensed
main program and license the whole work under the BSD, or the GPL,
or a proprietary license.

> but any copy-and-paste inclusion, modification and attribution might
> raise some eyebrows and/or compatibility issues (like I said, I'll be
> reading the fine print one more time to see if I can spot anything).

Indeed.  You cannot physically incorporate nontrivial amounts of
code (whatever is beyond fair use) from an LGPLed library into a
work with a license other than LGPL or GPL, and GPL only if you
convert that copy of the code irrevocably to the GPL.

--
John Cowan                              <cowan@...>
            http://www.ccil.org/~cowan
                .e'osai ko sarji la lojban.
                Please support Lojban!          http://www.lojban.org

[Smith, McCoy]

FSF put out a matrix relating to the compatability of various FSF
licenses:

http://www.gnu.org/licenses/gpl-faq.html#AllCompatibility

The answer on LGPL 2.1 + GPL 3 is a bit complex, and requires a
footnote.


-----Original Message-----
From: John Cowan [mailto:cowan@...]
Sent: Sunday, July 15, 2007 8:01 AM
To: Jesse Hannah
Cc: license-discuss@...
Subject: Re: LGPL 2.1 + GPL 3 = problems?

Jesse Hannah scripsit:

> Would using (linking, including/redistributing unmodified) a library
> that's licensed under the LGPL version 2.1 with a program that's
> licensed under the GPL version 3 cause any weird problems?

No, it would not.

> My initial guess is that just linking the libraries, or redistributing
> the source code unmodified---either entirely separate from, or
something
> like in its own folder in the same package with the GPL'd code---
> would be fine,

Quite right -- not because of the special features of the LGPL that
allow conversion to the GPL, but because the whole point of the LGPL
is that an LGPLed library can be combined into a larger work that
uses the library, and this larger work may have any desired license
consistent with the licenses of its non-LGPL components,
even a proprietary one.

For example, one may combine an LGPLed library with a BSD-licensed
main program and license the whole work under the BSD, or the GPL,
or a proprietary license.

> but any copy-and-paste inclusion, modification and attribution might
> raise some eyebrows and/or compatibility issues (like I said, I'll be
> reading the fine print one more time to see if I can spot anything).

Indeed.  You cannot physically incorporate nontrivial amounts of
code (whatever is beyond fair use) from an LGPLed library into a
work with a license other than LGPL or GPL, and GPL only if you
convert that copy of the code irrevocably to the GPL.

--
John Cowan                              <cowan@...>
            http://www.ccil.org/~cowan
                .e'osai ko sarji la lojban.
                Please support Lojban!          http://www.lojban.org

[John Cowan]

Smith, McCoy scripsit:

> FSF put out a matrix relating to the compatability of various FSF
> licenses:
>
> http://www.gnu.org/licenses/gpl-faq.html#AllCompatibility
>
> The answer on LGPL 2.1 + GPL 3 is a bit complex, and requires a
> footnote.

That matrix is useful, but it's about physically incorporating code
rather than constructing a larger work with LGPLed components, which
is what the OP was (mostly) asking about.  That remains no problem: an
LGPLed library combined with GPL version X components can and must be
released as a whole under GPL version X.  (If there are other components,
they must be compatible with GPL version X, of course.)

What's annoying is that GPLv2-only and GPLv3-only components cannot
be combined into a larger work.  Consequently, the original commons
of GPLv2 work is now divided into a GPLv2 commons and a GPLv3 commons,
with a large overlap due to dual licensing.

--
John Cowan  cowan@...  http://ccil.org/~cowan
And now here I was, in a country where a right to say how the country should
be governed was restricted to six persons in each thousand of its population.
For the nine hundred and ninety-four to express dissatisfaction with the
regnant system and propose to change it, would have made the whole six
shudder as one man, it would have been so disloyal, so dishonorable, such
putrid black treason.  --Mark Twain's Connecticut Yankee

[Matthew Flaschen]

Philippe Verdy wrote:
> What the LGPL says is that your modified library as a whole, licenced under
> LGPL v3 can be also licenced under GPLv3 only (excluding any later version
> of the GPL)

It does include later versions.  As noted earlier, it says, "(If a newer
version than version 2 of the ordinary GNU General Public License has
appeared, then you can specify that version instead if you wish.)"

, and in that case, the promotion of LGPL to GPL makes an
> explicit "additional restriction" to the default terms of the GPLv3 which
> normally allows by default "version 3.0 of the GPL or any later version".

The terms of GPLv3 do not allow using version 3.0 or later.  The license
notice usually (but not always) allows that.

Matthew Flaschen

[Matthew Flaschen]

Philippe Verdy wrote:
> Wrong! Not any version of the GPL, unless otherwise specified in an
> additional permission in the copyright notice of your library,

I noted in my earlier message why this is wrong.

> But if the FSF publishes a GPLv3.1 update but no update to LGPLv3.0 to
> authorize GPLv3.1

This is obviously unlikely.

> (2) Waiting for the FSF to publish a later version of the LGPL that allows
> using the library within a GPL v3.1 program. Note that "or any later version
> of the GPL" may be present absent from the updated LGPL v3.1, and if so, you
> won't be able to include it in the copyright notice of your program without
> asking for permission to the original author of the LGPL v3 library!

It doesn't necessarily have to be in the license proper.  It can also be
present in the notice of the LGPL program you're using.

>  But it may happen with possible future versions of the
> GPLv3, or with programs licenced by their original authors under GPLv3.0
> with additional restrictions such as those excluding later versions of the
> GPL.

This is not an additional restriction.  This is just licensing under
GPLv3.  The (or later) is an optional (but suggested) part of the
license notice.

This is a good thing too, because this is not an allowed additional
restriction in GPLv3.  It would be voided by "If the Program as you
received it, or any part of it, contains a notice stating that it is
governed by this License along with a term that is a further
restriction, you may remove that term."

> You CANNOT distribute your combined work under the GPL v2.1 or LGPLv2.1 if
> only one component is licenced under GPL v3.0 or LGPL v3, and this means
> that the new section about the required extension of Patent Licencing in GPL
> v3.0 will apply to your combined work.

This is not the only new section.

Matthew Flaschen

[Matthew Flaschen]

Philippe Verdy wrote:
> Note the exact statement is:
> "(If a newer version than version 2 of the ordinary GNU General
> Public License has appeared, then you can specify that version
> instead if you wish.)"
>
> But it is not cleared enough to explicitly state which "newer version" of
> the GPL is usable

Any of them are usable.

, notably because it does not explicitly say if it is
> valid.

Say if /what/ is valid?

  What makes the statement clear is "as published by the Free Software
> Foundation" in the copyright notice.

That is a useful clarification, but I think the main statement "a newer
version than version 2 of the ordinary GNU General Public License" is
sufficient, and implies only FSF-published versions count.

> These contestable terms (because it could include any other licence
> compatible with the GPLv2

I don't see how this is.

, including one containing some terms not published
> by the FSF itself)

It might be interpreted as accidentally including some rogue third-party
license calling itself GNU GPL v4, but I don't think this is likely

  were revised in GPLv3 (section 14) and LGPLv3, by
> explaining where such extended permission can be found:
>
> "If the Program specifies that a certain numbered version of the
> GNU General Public License “or any later version” applies to it,
> you have the option of following the terms and conditions either
> of that numbered version or of any later version published by the
> Free Software Foundation. If the Program does not specify a
> version number of the GNU General Public License, you may choose
> any version ever published by the Free Software Foundation."

This is present in both GPLv2 and LGPLv2.1, essentially unchanged.
GPLv2 says:

"If the Program specifies a version number of this License which applies
to it and "any later version", you have the option of following the
terms and conditions either of that version or of any later version
published by the Free Software Foundation. If the Program does not
specify a version number of this License, you may choose any version
ever published by the Free Software Foundation."

This is not the same as the statement in the body of LPGLv2.1 that
allows relicensing under later versions of the GPL.

> This statement explicitly makes additional restrictions to the future
> versions of the GPL (in the sense of section 10 of the GPLv3)

No, this is not an additional restriction in the sense of section 10.
If it was, it would automatically be voided, which makes no sense.

, as explained
> in the following paragraphs in that section 14 of the GPLv3.

Are you referring to "However, no additional obligations are imposed on
any author or copyright holder as a result of your choosing to follow a
later version."?

> This interpretation was confirmed by the FSF

What confirmation are you referring to?

>, and justified the need to include an upgrade to the referenced version of the GPL, to be fair with
> what was done with the LGPLv2 in the past (when used in combination with
> other non-FSF but compatible licenses).

I don't understand wh