It's not AI generated as far as my knowledge goes. And annoka mentioned that they don't mind the art being used commercially but because they used certain effects/brushes developed by others as apart of the artwork, there is a chance that the work is not 100% originally made (sort of like drawing your own background and then adding stock images for effect). So in a way, it's little bit more of a risk to use it in commercial projects. That's my interpretation at least