In The Emperor’s Name is a set of free wargames rules for skirmish games in the Warhammer 40K Universe. Theyr’e not up to version 3.0.
Aquanautica Imperialis is a set of rules for naval games in the world of Warhammer 40K.
Even if you don’t like the science fiction game, Warhammer turns out to be a pretty flexible system for playing other periods. Plus, it has the advantage of familiar mechanics and a built-in player base. So given that, its not surprising that it’s been extended to practically every period you can think of. Here’s a variant of Warhmamer 40K for colonial games in darkest Africa.
Rabbidgerbal’s Super Simple 1PG Sci-fi Skermish Rules is a set of free wargames rules meant as a 40K replacement.
Yes, that’s really how the author spelled “Skirmish”