It is a pretty grey area in the sense that I am not really sure what you are saying - if it is about creating an entirely new map -I am pretty sure that the answer is a no - it's not on.
If it is changing terrain - unless you are doing it in the scenario editor (which is pretty limited) - again, I am pretty sure that is not on too.
If you are talking about expanding an existing map -again, I am pretty sure that one is not on either...
However if you are talking about using the submap editor -which basically is text and typing in hex coordinates -then that is fine -but then again you only need to type in text for that -so, personally I don't get the impression that you were referring to creating a submap, however I will give you the benefit of the doubt.
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Mods -fwiw, the main issue with mods is that it seems like 90% of the guys doing them have no concept of copyright or public domain -yeah sure a nice plate from an Osprey would look great in the unit.bmp file - but the problem is one of it is not in the public domain. I imagine Osprey might not pursue guys doing this as a one off ... who knows, maybe they do - I sure as hell don't host any of that type of crap at SDC because I don't feel like dealing with cease and desist letters from lawyers.
I guess the larger point here is that no company that has two brain cells to rub together would ever mess with that sort of thing either - as you basically put the existence of your company in jeopardy -and why would anyone do that?
Otoh -to be fair I am pretty sure that I know one company that did slap an Osprey print on their printed and published gamebox -and the guy tried to get me to use it on his website (for the record I let that request go through to the keeper and -did not- use that image of some German stormtroopers running amongst British tanks in their Cambrai title ... interestingly enough Osprey doesn't seem to have gone after that guy -but that might just be indicative of how small time that boardgame company is -- no one probably brought it to their attention.
I guess what I mean is - if you want to experiment with this concept on your own - try hosting a sound mod with Elvis tunes in it -and see how long it takes Lisa Marie's legal team to get on to you

Or in other words - ymmmv - it is one of those, situations where as a business just does not find it worth the risk -and I never can understand exactly some people claim not to get this.
