The last official 1.x release of Adium was version 1.6.2c in September 2002; work on 1.x mostly stopped with the beginning of the development of a new version. This version, called Adium 2.0, is a complete rewrite of the code, and impliments such features as support for more IM protocols (such as ICQ, MSN Messenger, and Jabber) through the libgaim plugin. Adium 2.0 is in its alpha stages, and use of the alternative protocols is unstable as of now.
Most of Adium's functionality comes from plugins; the core program by itself does very little. The plugin system will allow users to pick and choose which features they want to include in the program.