I have recently emerged pychess on my gentoo system and have found out that not all users by default are able to play games, due to security reasons. If the game is istalled in “/usr/games/bin”, then only strusted users of the “games” group are able to play it.
# ls -l /usr/games/bin total 6620 ... -rwxr-x--- 1 root games 1290 Mar 20 08:13 pychess ...
The user can be added to this group by invoking the following command:
# gpasswd -a username games