[Karrot_Kream]

The thing is, compatibility with D&D wasn't necessarily about mechanics. Fundamentally TTRPG mechanics are really just about simulating probability distributions with dice. There's the broader question of how to use a given probability distribution where.

What D&D editions do is develop a set of base mechanics, basic probability distributions, and then create a framework on how to apply them. This includes monsters, races, and classes which have particular attributes or play feel. This includes common roleplaying conflicts and guidance on how to adjudicate them. What a lot of indie RPGs that used OGL 1.0/a did is they made references to things from D&D and used them in ways inspired by D&D. Think "elves" or "faeries" being associated with the mechanics and tropes you'd expect. Now with the new CC-BY-SA 5.1 SRD, you can make explicit references to Elves in derivative works and also license it under CC-BY-SA.

There were always completely separate systems that borrowed nothing from the play feel/world of D&D. Those communities/creators had nothing to fear.

[cma]

Ah thanks, I had thought the core thing was content agnostic.