After around 2,500 games, gnu was rated in the mid-1700s. This puts it somewhat higher than Abbott and Costello, although bots experience large ratings swings -- Costello has spent some time in the 1700s also.
The FIBS bot gnu is more than just another bot. It is a product of a wider-ranging, living project, GNU Backgammon.
Other bots based on the GNU Backgammon code are mpgnu and mgnutest.