|Eric Clingenpeel Venture-Captain, Michigan—Alma|
Actually, I think this might be covered in the GtPFSOP...
Additionally, a GM should have access to all booksin the Pathfinder Roleplaying Game line of hardcover
rulebooks, whether a physical or electronic copy. The
rules content of these books can be found online for free
as part of the Pathfinder Roleplaying Game Reference
Document located at paizo.com/prd.
Last I knew the GMG was in their line of hardcover rulebooks, so it is part of the core assumption for GMs. They've used other things from the GMG; stats, chase rules, other things I can't remember right now... So I say go for it! Use the rules Paizo has provided. Just tell him "GMs are not bound by the additional resources, which is why all the hardcover rulebooks are part of the GM's Core Assumption. Just because you can't use things found in it as a player doesn't mean I can't use rules in it as a GM. Scenarios use rules from it often enough."