ircII is a Unix IRC client that is made available completely free of charge, and is available in source form.
As the Unix and Unix-like systems evolved and increased in popularity, more, newer IRC clients have been developed for them as well. Perhaps the most common are EPIC, BitchX and ScrollZ, all of them variants of the ircII client with greater functionality built into them at some stage in their development.
At one time, the ircII client set the standard against which all other clients were developed and measured. While this may still hold true to some extent today, the Windows client mIRC has largely taken over that position, and ircII itself is under pressure from a newer text-mode client called irssi.