ToB and Publishing Question

[KellKheraptis]

What are the rules as far as publishing further support/content for non-SRD classes/systems?  I know WotC/Hasbro doesn't have the best track record for C&D, and would rather not sink my ship before it's left the port...

EDIT: I ask because all research as yet has been murky at best on the legality of it.  Anything explicitly SRD-based can be OGL/OGC-ed legally, but the further out there stuff is a different story.

[Skyrock]

ToB is a closed source. You can make references to it and write derivative original material, but you can't directly reproduce and quote text from it.

For a commercial release, you could consider Spheres of Power for Pathfinder 1E as a basis instead. It works very similar to ToB, but has been released under OGL and is freely available in the PF SRD.

[KellKheraptis]

I'm leaning more towards PF1e actually...kind of irked the links to publish there are broken, though that may be strategic (with PF2e an all).  Other than the stuff there, is there even much of a community for PF1e homebrew/3pp commercially?