WordPress MU is multi-user version of the famous WordPress blogging application. It is ideal for people wanting to offer a hosted version of WordPress, but due to its complexity installation and maintainance is not supported in the same manner WordPress is [link]
I wasn’t aware of this, and was surprised also that it is in active development. This would be a neat project to get my hands dirty.
UPDATE [6:01AM]: Installation and setup needs work. The support forum is very helpful, since THERE IS NO DOCUMENTATION. I think I’ll settle for a multi-blog plugin instead of this. Someone else from the forum has the same issue as me when I installed it locally.