Hypothetically, if somebody stole a quest and took it somewhere else and the original creator discovered it, there wouldn't be much they could do to have it removed(because who owns quests is questionable at best). If the license said it couldn't be there, they could easily have it removed by contacting the host.
Obviously, we decided against the one upload place edit in the license, but it may still be a good idea to list certain places. Here, pzc, etc.