One of the entries in the launchpad competition today was Sun Microsystem’s Project SocialSite.
It’s part of the larger Glassfish project, and uses Apache Shindig as an OpenSocial container – they demo’d OpenSocial widgets running inside Drupal and MediaWiki – all running inside a Java Application Server.
Video:
This could be a compelling option for those looking to run their own open social containers. It isn’t available in source code form yet, but you can sign up here to be notified when it is available.