Pidgin is a free and open-source chat client which supports AIM, Google Talk, ICQ, XMPP protocols.

Instantbird is a cross-platform instant messaging client based on Mozillas XULRunner and the open source library libpurple used in Pidgin.

Kopete is a multi-protocol, free software instant messaging client released as part of the KDE Software Compilation. Although it can run in numerous environme…

Tkabber is a GPL instant messaging client for the XMPP protocol which uses the Tk toolkit for the GUI.