Charles Roth MPC@hosh all seem to be converging but GS started out life as a microblog (twitter) like format. Diaspora as a social network (FB). Xmpp started as instant messaging, although it can certainly deliver to a larger chain of recipients and perform the mblog/social network function. Sadly, both FB & Google have restricted the access of outside XMPP accts recently.
Chirp! is a GNU Social instance for the Cooley and Sekula families and their friends.
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