From John Bafford:
ShadowIRC is a fast IRC client for the Mac OS. The program is extensible with C-coded plug-ins compiled with CodeWarrior. This makes ShadowIRC plug-ins faster and more flexible than AppleScript-based scripts, though you will need knowledge of C and a copy of CodeWarrior if you are going to write plug-ins. Among other features, ShadowIRC can process Ircle and mIRC color codes (though not at the same time). ShadowIRC 1.0.3 introduced better contextual menu support for plug-ins and improved performance, and the software has been recompiled with CodeWarrior Pro 5.0. In this version a new 'Search Backwards' option in the find window.