Where is the open-source social-networking site?

Is there one?

There are advantages to an open source equivalent to myspace of facebook: customisability for example.

There’s a few open source groups on facebook: http://www.facebook.com/home.php?ref=home#/s.php?init=q&q=open source group

Probably this one: http://www.facebook.com/group.php?gid=2257475215

I’m sure there many… but Facebook is NOT open source.