Like brogondwana says, from the commit log on their github repo, it's clear (years after that fastmail blog post) that Process One has abandoned ejabberd 3.x. ejabberd 2.x appears to continue to have updates. [0]
Having said that, for my single-account, single-site needs, ejabberd worked just fine for me for the several years between the time that I learned about the fact that Google Talk federated with XMPP servers and the time that Google stopped federating with other XMPP server operators.
I can't speak to how comprehensive ejabberd is, but for one-on-one chats, and multi-user chats, it worked just fine when I was using it.
[0] https://github.com/processone/ejabberd