The itch client claims that "No compatible downloads were found for 'OpenWar', so it wasn't installed." when I hit the install button on Linux Mint 18.3 (64Bit).
Downloading and installing the deb via browser works. I guess Itch doesn't like deb files.
After starting the game I downloaded the Shareware assets via menu and tried to run the game (menu item 0).
That gave me this output:
2018/07/18 20:22:04 Loading palettes... 2018/07/18 20:22:04 Loading images... 2018/07/18 20:22:04 Loading sprites... 2018/07/18 20:22:04 Loading tilesets... panic: missing timidity music decoder goroutine 21 [running, locked to thread]: github.com/andreas-jonsson/openwar/game.Start.func1() /home/travis/gopath/src/github.com/andreas-jonsson/openwar/game/start.go:115 +0x9f0 github.com/andreas-jonsson/openwar/game.init.0.func1() /home/travis/gopath/src/github.com/andreas-jonsson/openwar/game/start.go:52 +0x4c created by github.com/andreas-jonsson/openwar/game.init.0 /home/travis/gopath/src/github.com/andreas-jonsson/openwar/game/start.go:49 +0x35
After manually installing the timidity package I got it to run and successfully load a map.