diaspora* is based on three key philosophies: Decentralization, freedom and privacy. It is intended to address privacy concerns related to centralized social networks by allowing users set up their own server (or “pod”) to host content; pods can then interact to share status updates, photographs, and other social data.
Friendica has an emphasis on extensive privacy settings and easy server installation. It aims to federate with as many other social networks as possible. Currently, Friendica users can integrate contacts from Facebook, Twitter, Diaspora, GNU social, App.net, Pump.io and other services in their social streams.
While offering functionality similar to Twitter, GNU social seeks to provide the potential for open, inter-service and distributed communications between microblogging communities. Enterprises and individuals can install and control their own services and data. Notable public deployments are quitter.se and gnusocial.no.