Copyright law doesn't apply, and Gruber has probably lost any trademark rights when he failed to shut down the various Markdown flavours. I'm not a lawyer and

Copyright law doesn't apply, and Gruber has probably lost any trademark rights when he failed to shut down the various Markdown flavours. I'm not a lawyer and also not especially familiar with the laws in the US, but my guess would be that legally, he might not have a case. Of course there are also questions of morality, but who cares about that ;)