That depends. One case is someone really stealing and telling everyone "Ah, this is my map." Other, totally different case, is a fan of a map, that for many reasons, is unplayable, and the author did not resolve its problems, again, for a ton of reasons. Bugs that did not get fixed, imbalanced things, or as the case is, really unhostable thus unplayable because of the upgrade; in either case, said fan wanted to play a good version of the map. So, he does not have no choice.
You may say that both cases are equal, as both could involve a fan wanting to improve a map he likes. The difference that tells them apart, is that in the first case, the author is PRESENT and still able to upgrade the maps, and such, fix or add any features that the fan could just ask (although the author may not want to, and then the fan just steal it.), while in the second case the author is UNAVAILABLE to add or fix anything, thus forcing a good-willing fan to continue his work for the greater good.
Did that make it clear?