Yes, but that's not the same thing as it being easy to navigate. There's a whole area of copyright law on "derivative works" that does
not simply go away just because you paraphrase, no matter how many times people repeat "Copyright protects expression, not ideas" like a mantra.
Ideas
per se cannot be copyrighted. Individual words also cannot be copyrighted. But that does not mean that the novel
Jurassic Park is unprotected by copyright because it's uncopyrightable ideas expressed in uncopyrightable words. Nor can you run out and publish a translation of the book in French on the grounds that, by translating, you've paraphrased everything into new words. Nor can anyone easily and simply list what elements of
Jurassic Park are "copyrightable" on the grounds that Crichton was the first one to use them; the combination and arrangement of unprotected elements can itself be protected by copyright.
I've mentioned this elsewhere, but there's a reason that Sony settled the White Wolf lawsuit over
Underworld four days after it was filed, rather than fight it out; when you copy
enough ideas from a copyrighted work, any and all of the ideas unprotected individually, you're making a derivative work that infringes the copyright. And "enough" is
not clearly defined anywhere; it's a judgment call the court makes. Sony might well have won that lawsuit, had it been fought out, but White Wolf's claims were
not legally ridiculous.
Thus my specific example above of where the Pathfinder 2
Bestiary does the whole D&D devil/daemon/demon distinction. Or in a different thread, about the same
Bestiary covering ten dragon types distinguished by color/metallic hue matched with alignment, breath weapon type, and relative power. Or, as long as I'm grabbing examples from the "D" section of that work, drow who are underground-dwelling white-haired red-eyed elves who have a problem with bright light generally living in a society of chaos and evil, and duergar who are underground-dwelling grey-skinned size-changing dwarves who also have a problem with bright light.
Nobody's going to make a successful infringement claim based solely on the presence of a black-colored evil swamp-dwelling dragon that spews acid in a monster book. However, the "D" section of the Pathfinder 2
Bestiary taken as a whole? WotC has a solid -- not certain, but solid -- case if Paizo tries to distribute it under ORC, even if they used a system compeltely unrelated to D&D for the mechanics.
