One of the charming aspects of RISC-V is that it’s so… flexible. As an open-source processor specification, absolutely anyone can use it, modify it, and commercialize it. There are no licensing fees, no rules, and no compatibility test. It’s the Wild West of processors. Up to a point.
If you want to call your processor RISC-V, however, you have to follow the rules. The name “RISC-V” is trademarked, and there are also trademarked variations, subsets, profiles, and extensions that are all managed by the Switzerland-based RISC-V International organization. So, you’re welcome to ride off roughshod and blaze your own trail, pardner, but if you want to mingle with civilized company, you’ll have to tidy up and follow the rules.