sorry for answering only now, I was not on my box for two days. This is the error message when starting from command line (user tkrebs)
tkrebs@localhost ~ $ sauerbraten_client-bin
/usr/games/lib32/sauerbraten/linux_client: error while loading shared libraries: libGL.so.1: cannot open shared object file: No such file or directory
tkrebs@localhost ~ $
Can it be that it runs only on 32-bit?