for my site an year ago I writed a module for a java chat on irc server.
Now I want share this module.
It's an alfa version but it works
Some parts are only in Italian Language but if there's interest on it I can continue develop it.
You can try it here: http://www.e-socrates.org/campus/mod/ircchat/view.php?id=111
(for guest login click on "Login come ospite" then click on "Avvia la chat")
If you want try it on your server you can download it from
http://www.e-socrates.org/ircchat.zip (extract it on moodle root)
There are three params on admin:
ircchat_campus: base name for all irc channel (can be a fantasy name, ex "mysite")
ircchat_username_postfix: name to add to users' usernames for build unique name on irc server (can be a fantasy name, ex. "_mysite": the pippo user on irc server become pippo_mysite
irchat_server: important! the irc server name (ex "irc.freenode.net")
Thanks to all.. and sorry for my poor english 
Andrea Giardina