Chat Everywhere
Chat Everywhere gives you the possibility to easily put a real-time discussion forum on your website. It allows extended (Irc-like) commands, several levels of hierarchy and an easy to modify configuration file.

Chipchat
Chipchat is web chat program written in java language. It is web application and need web server such as Tomcat. It uses Applets on the client-side.

FreeCS
FreeCS is a free chatserver (WebChat) written in Java.

GujChat
GujChat is a new Chat System capable of managing multiple chat servers, each one serving different rooms and options for its users. One single installation delivers webmasters different templates, rooms, languages and configurations.

LlamaChat
LlamaChat is designed to provide an open source, chat server/client pair for use on the web. It is written in java and supports many advanced chat functionality including secure connections, emoticons, administrative class users, and more.

OpenCHAT
OpenCHAT is a 100% HTTP and HTML based chat server written in Java. It has it's own stand alone HTTP server integrated and does not need any Applet or special software on client side to run on, but only a frames enabled web browser.