You don't need any special certificate, accreditation, or license to make RPG stuff. Just do it. A lot of us older folks in the OSR get the label and I think we subconsciously follow that label that we are "The Establishment.  We aren't we're the underground comics. We're punk rock.  So let's go out there and make cool stuff and share it. Let others know about the cool stuff others are making. Personally, I have to get off my butt and get more done. More blog posts. More episodes of the pod cast. And just get a lot of that stuff that's been in my head out. And share it.