msgsd is a server-based replacement for the old Dynix "msgs" MOTD system tool. This reimplementation is designed as a single-thread discussion forum, similiar to a light-weight news group. As a server, remote users can participate in discussions as well. SSL connections are recommended.
Akeni Web Chat is an IM system designed for universal accessibility and ease of deployment. With its browser-based client, there is no need to install any client side software. It is also firewall friendly and can be used whenever you have access to a Web browser. The rich client supports chat, notification, and conferencing. It also allows your staff to provide real time sales information and technical support to your customer using a simple Web-based interface.
The Tcl IRCd is a small IRC server written in Tcl. It is very simple to modify. It is not a full implementation of the IRC protocol, but it's enough to create channels, talk in public or private, change topic, nick, and other basic operations. No configuration is required. The server is designed so that it can reload an updated version of itself at runtime without closing client connections.