OK, well the way I read it, the bit I quoted in my previous posts means “we may mention some of our products in the Open Game Content, but that does not transfer to you (or anyone else) any of our rights to said product identity.” And I understand it as that because of the first part of clause 7 as discussed previously, and also the bit under definitions that says: “"Open Game Content" means the game mechanic and includes the methods, procedures, processes and routines to the extent such content does not embody the Product Identity [...]"Product Identity" means product and product line names, logos and identifying marks including trade dress; artifacts; creatures characters; stories, storylines, plots, thematic elements, dialogue, incidents, language, artwork, symbols, designs, depictions, likenesses, formats, poses, concepts, themes and graphic, photographic and other visual or audio representations; names and descriptions of characters, spells, enchantments, personalities, teams, personas, likenesses and special abilities; places, locations, environments, creatures, equipment, magical or supernatural abilities or effects, logos, symbols, or graphic designs; and any other trademark or registered trademark clearly identified as Product identity by the owner of the Product Identity”
So in short you can include “This document contains the core Year Zero Engine for tabletop roleplaying, used in Free League games such as Mutant: Year Zero, Coriolis - The Third Horizon, Tales from the Loop, and Forbidden Lands.” because that text is part of the OGC, but I believe* it does not confer upon you the right to publish a game supplement with “My great game world, compatible with Forbidden Lands” or something like that, on the cover. You WILL be able to publish officially compatible content through the forthcoming Free League Workshop, though as you have discussed, that may contain clauses which you find objectionable.
*as always, I am not a lawyer, I may be wrong.
Effekt - A fan podcast celebrating Swedish RPGs including, but not limited to: Alien; Coriolis; Forbidden Lands; Symbaroum; and Tales from the Loop. Featuring discussion magazine episodes and Actual Play recordings. https://effektpodcast.org/