There's a prereq library, and things don't have the right permissions in the .rar. I pasted the whole process to the comments on the main page of this game.
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For anyone trying to install v2.0 on Linux: You need to install libpng12 (and maybe lib32-libpng12?) using your package manager. Then make the right files execuable:
chmod -x SQ2VGA_V2 Linux/data/ags*
Once that is done, you can start the game with:
It took me a little while to figure out why it wasn't working, so I thought I'd share for anyone else. It would be handy to have the right file permissions already in the .rar (or in the startup script) and personally I'd prefer a .tgz on linux. With any luck this will be fixed in a future release.