En le proceso de la busqueda, diseño e implantación de redes sociales me he encontrado con estas arquietecturas abiertas (GNU):
Social network
This is an academic social network application, which enables registered users to, select description tags, create profiles, create friendlists, upload photos, files, and create network groups and forums. http://sourceforge.net/projects/socialize/
Pligg
English translation of Mename, a Digg.com-like web site based on PHP and mysql. http://sourceforge.net/projects/meneame/
Akarru
Akarru is a social bookmarking engine, is used to build social bookmarkings sites, like www.blogmemes.com. Users posts links and promote links to front page using voting system. Akarr es un motor de promocin social de enlaces y blogs. http://sourceforge.net/projects/akarru/
Y otros mas como
AroundMe