LAN Messenger - LAN Messenger is a decentralized UDP IM-style chat client which supports usernames...
EchoWaves - Opensource Social Group Chat written in Ruby On Rails
MyChat - Secure instant messenger for any network
Shtuff Chat - Free Group / Team chat with persistent history.
BORGChat - BORGChat is a LAN messaging software program.
Anologue - Disposable online chat.