Regardless of the legal POV (I agree with Tim's point re: defensive trademark), I think it's not ethical to use the ERC name when your token standard hasn't been really tested and approved by the community. That's because many people think ERC = Safe. Which ofc might not be true if more people follow this path. Anyway, that's very clever: "I guess thats why it's called erc-404, like not found since it doesn't really exsist as a erc."