Pleroma : Pleroma is a federated social networking platform, compatible with GNU social and other OStatus implementations. It is free software licensed under th...
pump.io : Social server with an ActivityStreams API. It's a stream server that does most of what people really want from a social network.
freedom.js : freedom.js is a framework for building peer-to-peer (P2P) web apps. Easily create social applications that work in modern web browsers, Chrome package...
PeoplePods : PeoplePods is a developer-friendly social software toolkit
Build applications where people meet, talk, share, read, work, publish and explore.
GNU social is a continuation of the StatusNet project. It is social communication software for both public and private communications. It is widely supported and has a large userbase. It is already used by the Free Software Foundation.