just to let you know, we went for cgi:irc.
just like IRCG, it's the missing link between an irc server and a javascript frontend.
but ircg seems pretty much dead, you can't reach the author, can't even buy it anymore - cgi:irc is open source.
all you need is an ircd running, a bot, and minor modifications. chi:irc requires perl.
we tweaked it, so a doubleclick on a user name opens a window and so on, next thing would be putting chatters correctly on the who's online screen, but that can't be difficult either.