I think it is a general rule that you should first ask the maker of the map for permission to edit it. They can also give you an unprotected copy.
But if they do not agree to you editing it then you should not try to go behind their back and have some unprotect it for you.
In that case, you could learn to make your own Gods land from scratch (it's very easy to do).
The only thing you could do with the protected version might be to add new commands / jass code, but adding new objects/models/terrain would prove difficult. This is without actually breaking the protection, however.