[Zope] What is exactly Gruf ?

Hello, I'm looking a way to create many privates groups. What I mean is that each group is independent with its own private forum, documents, members, calendar, etc. I would like a user have the ability to belong one or more groups. I would like some users have the ability to register others inside groups. Finally, I would like a user log in and after he has the ability to choose a group to work with. (In fact I would like something like groove) I don't understand how Gruf works. Is it what I'm looking for? Thanks. Patrick Gelin