There was another (IRC) that I was using, for awhile, that was based on mIRC, but much more eye candy.. but can’t remember the name :P
I do remember that one of the creators of it was one of the creators of decentralization of sharing files (torrent style sharing).
PiRC? Wasn’t based on MiRC and diff language based scripting. Don’t remember which languages. It was a little slower than MiRC but scripting was more extensible with better scripting gui capabilities.