The way I see it, no one is likely to slap on a texture, model, etc., render it and make a ton of money from it. If their work becomes noticed and they make money from it, it's likely to be a labor of love with lots of time in it, lots of postwork, etc.

Trying to charge someone retroactively because their work becomes noticed isn't very ethical in my opinion. If you want to make money on it, sell it. If you don't care if people play with it or learn from it, let them do what they will with their renders.

It's common sense that the original texture, mesh, object, etc is the property of the creator and what we are discussing is a finished rendered product. It really surprises me how many people worry that a commercial use allowance will allow people to re-sell their mesh/texture/etc.

...... Kendra