You need the original game files to play.  You can purchase the game
on gog.com.  Install on another os and get a copy the "Data" folder
(rename it to "data").  Start the game once to create the config file
and point data_dir to the folder *containing the data folder* in your
~/.ja2/ja2.ini.

See ja2(6) for more information.

You might get hit by a SDL bug affecting the behaviour of the mouse
cursor, so to start the game in fullscreen, you can use
`SDL_VIDEO_X11_DGAMOUSE=0 ja2 -fullscreen'.