The difference is free. No quid pro quo.
I think you have the right idea by asking in advance.
Last year, for S&G's, a member here called an individual who posts here as a coach and asked about a lesson at Breck. The "coach" was good to go......quoting a price.
I taught four days last year at Vail in a Winter Park uniform. My client paid for the lesson through the Winter Park ski school and Vail provided me with a lift ticket and line cutting. All of this done throught the ski school director. We afford the same opportunity to Vail instructors at our place. All they have to do is call ahead.
I can assure you that there are individuals who are former WP instructors that will have their ticket pulled and be run off if they appear at WP and even look like they are teaching.
No need to mention any names.
I too taught at other areas in uniform when I was teaching and the accepted manor is exactly as you discribed above.
My concern is the APPEARANCE of something like Cubefest or any other free clinic I or others may throw...or using GUIDES if something like Let's Go Colorado were to ever be held again. Sure, we here understand there is no money exchanged, but would Vail Resorts ?
I think in the future I would now feel compelled to ask permission from the areas to use guides at an event like LGC or ask if we could hold a free clinic. My expectation would be that LGC would not be a problem, but teaching a free clinic to EpicSki members might not be allowed even though we would not be taking a customer away from their school.