Although I don't have the answer to your question about licensing I can tell you what we did.
We had a customer that wanted his truck wrapped in camo, mossy oak to be specific, so after looking at their files on the net and not wanting to go through a licensing fiasco, we took one of our digital cameras out to the wood took about 20 shots that looked like their graphics, came back home and made our own version.
Turned out great because all of the mossy oak we looked at the pattern reoccurred much too often for our taste, the pattern we made looks very much like mossy oak but doesn't reoccur or repeat as often.
Hope this helps.