There is a section of copyright law in the U.S. known as "substantial similarity" that can be used to accuse someone of copyright infringement if the work in question is similar enough in "look and feel" to the original. It's a vague and kind of scary thing that seems like it could be leveraged easily by anyone with a good enough lawyer. So many RWS based decks could potentially be taken off the market if US Games decided it was going to pursue the creators/publishers of every tarot that is substantially similar to the RWS. To my knowledge, no copyright holder of Tarot decks has ever done so. I'll admit it's not like I pay THAT close attention, but it seems like something like that would cause ripples in the Tarot community.
There's something called the idea-expression divide that may give Tarot creators a bit of protection. Basically, because ideas cannot be copyrighted, we only have to make sure we don't infringe on an existing tarot's expression of the idea. Still, where the line falls between idea and expression is blurry, specifically in the Tarot world. The Fool as an archetype for new beginnings is an idea that can be expressed in many ways. The image of a vagabond and his dog on a cliff is an idea that can be expressed in many ways. But the RWS for example *expresses* the idea of the Fool archetype as a vagabond and his dog on a cliff. Seems to me like yet another vagary in copyright law that a lawyer could potentially exploit.
All that said, it seems to me that the players in Tarot publication are ethical enough not to sue for copyright infringement based on substantial similarity. In the case of the Thoth Tarot, I can think of two decks - the Liber T: Tarot of Stars Eternal and the Rosetta Tarot - that could easily be accused of substantial similarity to the Thoth based on some (or many) of the cards in those decks. Half the battle of suing for copyright infringement is proving that the accused creators/publishers had access to the original work when they created their new work. The Liber T and the Rosetta were publicized by their creators as being inspired by the Thoth, so that part of the battle would already be won by OTO should they ever decide to sue based on substantial similarity. And yet both those decks are still out and about and being enjoyed by the Tarot community. Unless the creators of those decks were given explicit permission to create what could be argued to be derivative works of the Thoth, it seems that the OTO is above suing artists for creating Thoth-similar works.
) so was thinking to try it out on Thoth Tarot?x,x as it seems interesting and it would give me a chance to work with it more and learn more about it?x,x