Wikipedia
WeeChat
WeeChat (Wee Enhanced Environment for Chat) is a free and open-source Internet Relay Chat client, which is designed to be light and fast. It is released under the terms of the GNU General Public License 3 and has been developed since 2003.
WeeChat comes with a default ncurses interface, but it is possible to use other interfaces (e.g. Glowing Bear, a web frontend).