The SocialSite software is an OpenSocial container that can run any OpenSocial application built using the associated specifications:
The SocialSite software has added extensions that have been defined according to the OpenSocial specifications so that any extra person, activity or other object fields is defied in such a way that allow OpenSocial applications to discover these fields. These extensions are specific to the SocialSite container:
People and friendships
User profile data
User profile privacy
Group management
Gadget management
Messaging
Search
A SocialSite widget is an OpenSocial-compliant gadget that calls one or more SocialSite-specific extensions.