AnonyNews comes in two parts- Server and Client. The server must run under Linux, but there is a GTK client for *nix systems and a Java client for any system including Windows.
The Server runs as a daemon, listening for Clients that wish to communicate with it. It looks after the storage and distribution of messages.
The GTK Client runs on the user's machine, and must have X running, with gtk+ libraries loaded.
The Java Client runs on the user's machine, and must have the Java RunTime Environment loaded.
The Clients do not work in an offline mode, so a connection to the server must always be present when sending or reading messages.