Pre-release snapshots of GNU Backgammon are periodically made available for FTP at ftp://alpha.gnu.org/gnu/gnubg/.
If you want to experiment with the very latest code, the development sources are kept in a CVS repository at http://subversions.gnu.org/cgi-bin/cvsweb/gnubg/; see the @gnubg{} web page at http://www.gnu.org/software/gnubg/gnubg.html for instructions on checking out sources from the repository. Daily snapshots of the main branch of the repository are automatically placed in the `snapshots' directory of the FTP area above, if you wish to retrieve this experimental code via FTP.
Once you are running @gnubg{}, enter new game at the `(gnubg)' prompt to start a game against the computer opponent. You should now see a board (if a window system is available, @gnubg{} will use a graphical board window; otherwise, it will display an ASCII board on your terminal). If @gnubg{} won the opening roll, it will have moved; you can now type roll (or click on the dice below the board window) to roll the dice yourself. In either case, it will now be your move; you should enter the moves for each chequer as pairs of numbers. For instance, if you have rolled 3 and 1, you could type 8 5 6 5 to move one chequer from the 8 point to the 5 point and another from the 6 point to the 5 point. Use bar to move from the bar, and off to bear off. If you are using the board window, you can also drag chequers around the board. Click on the dice when you have finished.
The file `gnubg.bd' is the bearoff database that @gnubg{} uses to evaluate endgame positions. @gnubg{} will look for it first in the current directory and then in the installed directory (`/usr/local/share/gnubg/' by default).
The @gnubg{} distribution is set up to create `gnubg.bd' by itself during compilation, but it can be a slow process (taking half an hour or more, depending on the speed of your computer). If you would rather not wait to generate the database yourself, you can obtain a copy via FTP from ftp://alpha.gnu.org/gnu/gnubg/gnubg.bd.gz.
FIXME this is out of date; gnubg can cope without gnubg.bd if it has to.
The file `gnubg.weights' contains the trained neural net weights for most of @gnubg{}'s position evaluators. Like `gnubg.bd', it should be kept in either the current directory or the installed directory.
A binary variant of the weights file named `gnubg.wd' can also be used (this version can be loaded more quickly, but is not portable between different computer architectures). It will automatically be built during the compilation process, and used in preference to `gnubg.weights' if found.
You should be able to obtain a copy of the weights from wherever you found the @gnubg{} distribution. If you wish to start @gnubg{} without any weights (and train your own), you can use the @option{--no-weights} option (see see section Invoking @gnubg).
If you see this problem, your X server is probably using a PseudoColor visual, and is dynamically allocating colours to clients from a limited colourmap. On these types of displays, @gnubg{} tries to be a well-behaved client by using colours from the default standard colourmap. This will allow it to share colours with other clients that use the same scheme, which will help them all to use as many colours as possible without exhausting the colourmap.
Unfortunately, not all X clients use standard colourmaps. If other clients have been run before @gnubg{} and allocated most of the colours, then there may not be enough left for @gnubg{} to allocate a standard colourmap. If this happens, it will just take what it can get (which in the worst case might be black and white only). You can try to avoid this problem by running @gnubg{} before other colour-hungry clients, or by using the `xstdcmap' utility to install the default standard colourmap early in your session while colours are still available. Depending on your hardware, you may be able to configure your display to allow more colours, or use a DirectColor or TrueColor visual which should resolve the problem.
Of course, if your X server can only display black and white (not even shades of grey), then there's not much you can do!