Hi Duncan - another option is matrix.org - we're similar to XMPP although at the same time different: Matrix is effectively an eventually consistent DB with open federation and pubsub semantics - it's all about synchronising state, whereas XMPP is about federated messaging - sending stanzas around rather than synchronising conversation history.

In fact in Matrix we don't even have the concept of sending a message over federation - the only thing you can do is to synchronise the history datastructure.

We don't see Matrix as undermining XMPP: if you want decentralised conversation history then use Matrix. If you want fast stateless message passing, use XMPP. Infact, we're building an XMPP<->Matrix bridge, so that XMPP can federate with Matrix - so it's not like we're fragmenting things further. The point for Matrix is to try to defragment all the different protocols out there.