The topic of rights and intent of use of challenge maps was brought up in the discussions with the annual challenge, if I recall correctly, and though I'm not sure if it was ever actually stated as a solid rule I at least took it as an informal understanding or agreement that such maps should be created for the challenge alone and not a third party, though it could be used for other purposes after the challenge. At least, that's what I remember of that subject of the conversation. Someone else will likely have a better answer. I hope so anyway, as I'd like to understand it better. Seems weird in some respects, and makes sense in others.

There does appear to be a clear instruction in this challenge to pretend you have been commissioned, but it also has been said that you can create a map for an existing novel. I don't know, but I'd say it makes sense that if you have the right to use and show the map in the challenge and it meets all of the requirements then there's not much difference. But, challenge rules aside, it depends on the terms of the commission and your agreement with the author if you have the right to, or should, reveal the map before the book is published.