Xchat

An pluggable, skinnable, themable IRC client for UNIX and UNIX-like operating systems, including OS X. CLI and GUI versions. It should be easy to use for people familiar with Windows clients such as mIRC. It has a tabbed multi-server interface and has a long list of features that leaves little to be desired. An experimental Windows port is available.

Open-source and distributed under the GPL.

TakeDown.NET -> “Xchat”