Another thing to consider, maps produced by forum members intended for publication, that are co-opted by other cartographers here without permission for their own projects require the permission of both the original cartographer and the publisher - and often the answer is "no". Mike Schley is one of our renowned members doing lots of cartography commissions for Wizards of the Coast, often for D&D maps. Any of those maps posted here, cannot be reposted elsewhere or used in personal projects at all. There was a case where some new member here wanted to base a town on the style of Mike Schley, but literally used one of his maps to alter for his own purposes, but that member reposted his altered version on the forums. Mike Schley showed up and asked it to be removed from the boards and had the issue not been resolved a cease and desist order from WotC attorneys may have been the next recourse. So it depends on who the cartographer is, what is the intended published purpose for a given map, and who the publisher is - whether you can do derivitive work from maps produced by other cartographers.