Vague? What part of the clause "other product without explicit prior permission" is vague?
What's vague is whether "advertise, promote, present, or sell" includes "create". My gut feeling is that Martin's intention is that it should, but I have no idea what a court would say.
Anyhow, the primary market for such videos would probably be Orbiter users, and regardless of the legalities, the controversy over monetized Orbiter videos would likely kill sales.
---------- Post added at 12:36 ---------- Previous post was at 11:58 ----------
well, from what i was taught in my copyright law class in college, this could quite possibly fall under the "composer/interpreter" scenario....
where the person who makes the video is an "interpreter" creating a new piece derived from the work of the "composer", which is Martin in this case...
the law is quite clear on that - BOTH parties are entitled to gains, in a percentage which i fail to remember (and possibly differs denepnding on the situation)
With regards to making videos with Orbiter showing only meshes and textures made by the person making the video, I wouldn't want to even touch the composer/interpreter scenario. 'Cause if you allow Martin to charge royalties on videos made with Orbiter, you allow Microsoft to charge royalties on books written using Microsoft Word. (I don't have much problem, though, with the use of a freeware license for non-commercial use, and a payware license for commercial use, or simply forbidding commercial use entirely).
Of course, the whole situation changes if you're using stock orbiter meshes and textures in your video, or if you're using 3rd party addons. Then it's equivalent (in the "stock orbiter meshes" scenario) to using Microsoft clip art in the book you write using Word (I'm not certain how MS licenses their clip art, but they certainly could charge royalties on its use), or (in the "3rd party addons" scenario) to writing Luke Skywalker into your book (in which case George Lucas would probably drop by looking for a royalty check).