What's the difference between forum, mailing list, blog, news, photo gallery, document library, knowledge base, FAQ and comment?
To Nabble, they are all the same node structure shown in different views.

A forum is the same node entity as a comment, in that they both have a title (forum title = comment subject), a body (forum description = comment body), and an author (forum creator = comment author). In this sense, a forum and a comment are also the same as a post, a blog, a blog entry, a photo entry, a news entry, a reply, etc. They are just nodes shown in different views. Each node inherits the same set of functions: search, subscription, feeds, user access control, moderation, embeddability, cataloging, threading and descendant views, among others.
What's more, this universal node-oriented back-end is scalable because it's distributed. User accounts and search are shared by all machines.

With this universal back-end structure, Nabble can build or customize a web app very easily. All that is involved is some front end programming. And all apps are naturally scalable, searchable and embeddable.
If you like this universal back-end, please let us know. We plan to release Nabble as an installed application, so that your site can take advantage of a full suite of web apps using the same simple code already tested by millions of visitors at our main Nabble website.