GNU Backgammon is a project initiated by Gary Wong (firstname.lastname@example.org, GaryW on FIBS, URL: http://www.cs.arizona. edu/people/gary/), author of Abbott and Costello. The project is interesting in that it seems to emphasise open, collaborative development (UNIX users will be familiar with the GNU ("GNU's Not UNIX") and FSF ("Free Software Foundation") licensing concepts). As far as I'm aware, this is the first open source backgammon project (the open source movement is captured neatly in Eric Raymond's paper The Cathedral and the Bazaar), and as such has great potential.
The project's Web site contains more details and has a pointer to the source code for GNU Backgammon.
An early product of the project is the FIBS bot gnu. Other bots based on the GNU Backgammon code are mpgnu and mgnutest.