パッとみて、使い方ｻﾊﾟｰﾘ分からないけど、
これって使えそう？
OS9もOSXも使えるみたいだが(Winも)

Pexit is a multi-platform IRC client featuring an intuitive GUI interface, concurrent
connections to multiple servers, color support, and smilies. It supports DCC ransfers
and automates DCC file searches and downloads on IRC. Pexit also supports other
chat and file-transfer protocols, which co-exist seamlessly with IRC. Download it
free at www.pexit.com

Pexit is a multi-platform, multi-protocol application. It seamlessly implements popular
chat and instant messaging protocols such as IRC and TOC, as well as having its
own versatile protocol which allows text, audio and video chatting and a graphical
whiteboard. Also, Pexit features its own peer-to-peer protocol, and supports others,
including OpenNap and gnutella. Pexit is written in Java, is plugin-in based, and has
an open API. It fully supports the addition of third party plugins. Download it free
at www.pexit.com