StatusNet (formerly Laconica) is a FLOSS microblogging server written in PHP that implements the OStatus standard for interoperation between installations. While offering functionality similar to Twitter, StatusNet 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. Stable release http://status.net/statusnet-0.9.9.tar.gz Development release http://status.net/statusnet-1.0.0beta3.tar.gz
Joining the "interested" party
Seems dead now.