I recall hearing about the difficulties with getting at least one older shareware version of SW (1997) to run; Good to see this is resolved.
As for obtaining the full version, it has been available from Devolver Digital on Steam as a "Free to Play" title: http://store.steampowered.com/app/238070/
Once downloaded, you basically get the game with OGG files for the music and a DOSBox setup.
While it lacks the two add-ons of "Wanton Destruction" and "Twin Dragon", these were originally (and still are) available for no cost from various sources, although you may have to mess with a DOS installer and the like in order to get any of these to work.