Gobby is a cross-platform open-source collab-editor. It is the core tool for a ting (ting-wiki: ting 52 sunday 26th of March 2006 19:00 French time for example)
see crao-wiki: gobby (in French)
Gobby ain’t perfect yet. It’s bleeding-edge software. To understand it’s capabilities you have to try it out.
Installation on Windows and Linux is fairly easy. gobby-wiki: installation guide, English, all plattforms
Installation on Mac
There is also gobby-wiki: how to compile gobby from source / MacOSX, English