Italk.el is a client of the italk chat system, running on mule 2.x (a multilingual extension of emacs, based on 19.x) and emacs 20.x. It works under both X window system environments and character-based terminals. Windows ports of emacs (mule for Win32 and Meadow) are also supported. Italk.el is easy to install and user-customizable by ~/.emacs setting.
More description (document) is here.
There are some branches of italk.el. Here currently presents the main-stream "Tak. version" of italk.el.