I've been watching open source microblogging engine, StatusNet, for sometime and blogged about it back in 2011. Status.net also powers identi.ca, which was the open alternative to Twitter before app.net grabbed all the attention.
In December, Evan Prodromou announced that he was winding down the hosted Status.net service to concentrate on a new activity stream server, pump.io. The back-end of identi.ca will eventually be migrated to pump.io too.
What is pump.io? Pump.io is still in its very early days (the latest build is 0.2.1) and Prodromou is a little light on plain english documented details:
"It's a stream server that does most of what people really want from a social network."
The new architecture of Pump.io still supports federation but also creates the potential to develop new distributed applications and even distributed advertising models for commercially run pump.io networks. If you download the source, the API read me file outlines the technologies being used, including Activity Streams for data format and OAuth 1.0. An example application is OpenFarmGame.
This is quite a pivot for StatusNet, but clearly for the small company behind it this make a lot of sense if they want to leap frog from their old code base to something new.
BTW this doesn't mean that the StatusNet software is dead. In a clarification comment, Prodromou explained:
"StatusNet the software will continue to be developed and supported. StatusNet Inc. has commercial agreements with some companies using the software and I intend to honor those agreements."