If you go the the ajax chat main download page, get the one for phpbb3.
There are some documents on how to integrate to the board on that site, but i personally never used those ones.
I have however used another one from a while back adds the AJAX chat into phpbb much like mchat.
I'll post the mod authors profile form phpbb.com I hope that is ok
you can follow his website link and you'll find some snippets for ajax chat. https://www.phpbb.com/community/memberl ... e&u=148403
It used to be posted on old SourceFordge fourm spot.
It's an old snippet but it may still work for 3.0.11... right off the bat I can't see why it wouldn't.
anyway, hope it helps someone who is looking for an mchat alternative