Right. If anything is the "Linux of courseware" it's Moodle.

Personally, though, I think the whole concept of a "course management system" goes away in time.

BTW, we've been using Opensimulator: http://opensimulator.org/wiki/Main_Page for synchronous sessions and collaborative projects, and it works pretty well. Croquet: http://www.opencroquet.org/index.php/Main_Page and Project Wonderland: http://openwonderland.org/ are also worth a look.