Pidgin is a free and open-source chat client which supports AIM, Google Talk, ICQ, XMPP protocols. Developed by Pidgin
License: Open Source
Kopete is a messaging application primarily designed for the KDE desktop environment, offering strong integration with it but limited protocol support and development. Pidgin, on the other hand, is a cross-platform application with a broader range of supported protocols and a more active community, making it a more versatile choice for users.