Amethyst started as a port of Infobot to POE, continuing as a generic bot core with the ability to handle multiple connections using different protocols (not necessarily IRC) and soft route the incoming messages through a number of processing centres. One of these processing centres contains much of the original Infobot core.
BBSzilla is an extension for Mozilla-based browsers such as the Mozilla Application Suite and Firefox. It gives the browser the ability to connect to Bulletin Board Systems that utilize TCP/IP, such as Hotline servers. There is functionality for multi-user chat, single-user messaging, as well as server-side and P2P file sharing, threaded news, single-thread bulletins, and more.
Citadel is an advanced messaging and collaboration system for groupware and BBS applications. Users can connect to Citadel using any telnet, WWW, or client software. Among the features supported are public and private message bases (rooms), electronic mail, real-time chat, paging, shared calendaring, address books, mailing lists, and more. Unlike other collaboration servers, Citadel provides its own data stores and is therefore extremely easy to install; you don't have to "bring your own" email and database because they're built in. The server is multithreaded and scalable. In addition, SMTP, IMAP, and POP3 servers are built-in for easy connection to Internet mail. Citadel is both robust and mature; it has been in production since 1987.