From DOS ain’t dead: the game was added to battle.net as a free download (1,2).  But you don’t need a battle.net account to download it, just get the ‘executable’ here.

Then unpack with 7zip and rename some files:

$ mv _7770311E01264484BDC66FB81E4EF650 blthorn.exe
$ mv _126448A72F4442D39DCD600746EE09F7 data.dat
$ mv _C987F762EF304955BB86AB432FF6F847 manual.pdf

I set DOSBox to run about 20,000 cycles so it’s not tooo bad.