In addition to certification trademarks and limited uses via "trademark guidelines" there's an interesting counterpoint in the case of Portal: Prelude. Valve p

In addition to certification trademarks and limited uses via "trademark guidelines" there's an interesting counterpoint in the case of Portal: Prelude. Valve permitted (at the very least a verbal license) an independent developer to use their trademark (and other assets) in an unrelated project not controlled by Valve. I'm very curious on the line of thought of Valve's lawyers as to how this would be ok. Perhaps it's because Portal: Prelude requires Portal to be purchased in the first place and therefore doesn't actually compete with Portal?