I think you're best asking a lawyer, to be sure.

But from what I, random citizen, have looked into the matter out of curiosity, apparently they're a grey zone, usually overlooked, ignored or accepted. But while you'd be sharing differential code, not the protected code itself, you needed to break a patent by reverse-engineering the game, which for draconian laws like the DMCA, is potentially worth even federal prison. Plus for others to apply the mod, they'd need to break the patent too by using the tools you indicate.

And there are cases where the game has official modding tools or that the devs explicitly say they're fine with mods. In such cases, I'm fairly sure worrying isn't needed.