enemy territory is a 32bit application, your profile shows you are running slackware64, so you first have to go
multilib to run it.
EDIT: sorry, just tried, same problem on multilib, maybe a problem with the installer: I'm preparing you a folder to download
here it is (EDIT: removed. prepared package. look down in thread)
just uncompress in /opt, you will have an "et" folder that contains the game.
if you like, copy the /opt/et/et shell script to /usr/local/bin or elsewhere in your path, then start the game from console with
if you like it elsewhere than /opt/et just edit the paths in the et script.
P.S. if anyone knows of any problems hosting such a thing, please tell me, don't want to do anything "strange".