What is "pump.io"

Pump.io (pronounced "pump eye-oh") is a general purpose activity streams engine that can be used as a federated social networking protocol which "does most of what people really want from a social network". Started by Evan Prodromou, it is a follow up to StatusNet; Identi.ca, which was the largest StatusNet service, switched to pump.io in June 2013. However, while StatusNet offered functionality similar to Twitter, pump.io offers much more general purpose social networking, and is being adopted by other types of web applications, such as MediaGoblin.