As a new member I struggle to fully understand this concept. It's not so cut and dried for new people that haven't been exposed to this before. Clearly something you've done is covered but what about the stuff in "free paper props". Customers can come into an office products store and copy copyrighted stuff for "fair use". But what is the "fair use" of free ? If I physically give you a Jumanji dice that I make (still working on it) you can then turn around and sell that physical object if you wish without consulting me. But not make exact copies and sell the copies without my permission. To me, there is a difference in calling the forum FREE paper props. Logically, that implies LESS protection.
I work in an office products store. I have to refer people to self service if they want to copy copyrighted material. But it would be absolutely legal for ME to print anything that is here in the "free" paper props section and sell it to the customer. Free means free legally. Free is the opposite of copyrighted. I can charge people to print anything that is in the "free" section. That is what the LAW says. If you don't like the law, then don't put anything in the free paper props section.