Discovered for myself this today
http://sourceforge.net/projects/gaim/ but I don't know how well it
compares to trillian yet.
As far as IRC clients go, both of them are pretty weak. As far as
multi-protocol clients in general, both Gaim and Trillian have their
strengths, but at least for me the weaknesses outweigh the strengths.
If your'e looking into a multi-client chat app, you may also want to
look into MirandaIM (
http://miranda-im.org ). It's free and has a
pluggable architecture which makes it very modular, and at the same
time very powerful. It even has an IRC plugin which you can get at
http://miranda-im.org/download/details.php?action=viewfile&id=550
I haven't used that plugin at all, so I really can't vouch as to it's
ability. However, one thing that's also great about Miranda is that
it has a very active developer community as far as both base
functionality and third-party plugins.
Just my 2 cents.
