YaCS is a modular community framework server for Web clients, providing a feature-rich chat, multiple identities, guest books, multiple communities, and more.
WeIRCd is a robust, simple, and easy-to-use IRC daemon. Its built-in services make setting up Chanserv, Nickserv, and others very easy. The server supports runtime loaded modules and other modern features.
A membership management system.
Public domain general-purpose libraries.