Based on his interaction with the CommonMark people I would characterize it more as overly possessive.
As someone who contributed a bit to the early CommonMark spec I think some of us were really doing it the shitty way towards Gruber.
How would the Rust people react if we created a "Standard Rust" language?
https://daringfireball.net/projects/markdown/
>Markdown is free software, available under a BSD-style open source license.
John Gruber's markdown is unmaintained (last updated in 2004), free software, which many people have contributed to to fix oversights and extend its capabilities. This is exactly how fsf is supposed to work.
It was about the _Name_ , never about the syntax/implementation.
Gruber was very clear with his license and regular words that he did not allow the usage of the name in a manner which would cause people to be confused or suggest that it was an official implementation.
You could maybe patent Markdown (given the amount of trash software patents I've seen I wouldn't be surprised) but (1) it's not patented AFAIK and (2) it's become so common (mark, heh) that I don't think it could be patented anymore.
You could say Markdown is covered as a trademark even if not officially registered maybe? I don't know the specifics though, could anyone chime in? (this is complicated further by the different jurisdictions). But my understanding of the general idea is that if your trademark becomes common (which I guess happened?) or you don't actively defend it (which is what Gruber was trying to do fighting Standard Markdown), you lose it.
So, to summarize, I think he was right to be angry (in a moral way) but that's possibly the only right he had in the literal sense. Which is more than enough of course.
If the crucial part here is the fact that he apparently already copyrighted the name then that seems kind of like begging the question. I wouldn’t copyright a bland name like that which has no connection to my own person. (Maybe I would copyright something like keybord-lang though...)