You can download this free classic version from its respective GOG Store page. You’ll get both official expansions (Wanton Destruction and Twin Dragon) as well.
GOG also released Shadow Warrior Classic Redux on the same day, but unfortunately without Linux support, so if you prefer this enhanced remake, you will have to go to Steam. Plus, keep in mind that you’ll have to pay for this newer version.
About the game (Official)
From the creators of Duke Nukem 3D, comes the ever-explosive, forever controversial Shadow Warrior, a first-person shooter that takes the Build engine to its extreme limits. Offering a destructible environment with a bevy of weapons--ranging from razor-sharp katanas, 4-barrel shotguns, and even your own fists--Shadow Warrior is sure to satisfy the hunger for some Lo Wang and not leave you hungry an hour later.
Shadow Warrior Complete includes the original Shadow Warrior and two expansions: Wanton Destruction and Twin Dragon.
-Drivable vehicles smash through walls, crush enemies, and give you new explosive firepower!
-Use a powerful arsenal of weapons, including throwing stars, uzis, and 4-barrel shotguns to take on the most outrageous collection of enemies ever created.
-Hand to Face combat mode lets you kick butt and slice 'n' dice in true ninja fashion.