Kevin Crawford’s old-school RPGs, which he puts out through his Sine Nomine Publishing small press, have been one of the most interesting pillars of the OSR scene for about a decade, ever since the release of Stars Without Number.
Rather than being based on a retro-clone of a specific D&D edition, Stars Without Number drew its system inspiration from a mixture of OD&D, B/X D&D, and Traveller. Its choice of D&D influences means that the system broadly resembles something like the sort of “rationalised” D&D system that a talented referee might have worked out at their home table from the OD&D rules set, had they taken the lighter approach of the Holmes-authored Basic Set or Moldvay and Cook’s B/X distillation of the rules instead of the crunchier approach taken by AD&D. (To a large extent both Advanced and Basic D&D represent different approaches to clarifying and tidying up OD&D.)
The Traveller input in Stars Without Number is most immediately obvious on the choice of setting and genre rather than the system side of things – both games are about crews of starfarers gadding about in a hard-ish SF universe – but there are also some important system aspects there. The inclusion of a Traveller-style skill system adds a welcome resolution mechanic to proceedings and makes the early D&D approach feel like it offers a bit more character definition outside of the immediate dungeoneering tasks of fighting, magic use, and exploration. In addition, the extensive use of random generators to help the referee generate material for the game is both a feature of Traveller and has become a hallmark of Kevin Crawford’s games.