Anyone can implement a compiler or interpreter for C# if they want, and there is a link to the standard for it. Is this clear enough for you?
Also, from an earlier comment you made a false claim and a strange reference.
You claimed that "most of" Java, Rust, C#, Python, and Go have only a single implementation. This is false. There are multiple implementations of each.
Second, you make a bizarre reference to "fad[ing] away like Pascal." Why do you think Pascal faded? I'll give a hint: It had nothing to do with being proprietary. At best that reference is a non sequitur, at worst it demonstrates more confusion on your part.
It isn't my reading comprehension that is deficient. You are talking in circles and demonstrating a remarkable inability to think clearly. I was just being polite.
Something being proprietary means that it is owned. It means "relating to an owner or ownership"; "of, relating to, or characteristic of an owner or title holder"; "used, made, or marketed by one having the exclusive legal right"; "privately owned and managed and run as a profit-making organization."
You claim to be a lawyer, I doubt your reading comprehension is really this bad but just in case I'll spell it out for you. You asked:
> More importantly, is there a public body that owns the spec?
And I answered:
> For C# there is the ECMA specification for it https://ecma-international.org/publications-and-standards/st...
Anyone can implement a compiler or interpreter for C# if they want, and there is a link to the standard for it. Is this clear enough for you?
Also, from an earlier comment you made a false claim and a strange reference.
You claimed that "most of" Java, Rust, C#, Python, and Go have only a single implementation. This is false. There are multiple implementations of each.
Second, you make a bizarre reference to "fad[ing] away like Pascal." Why do you think Pascal faded? I'll give a hint: It had nothing to do with being proprietary. At best that reference is a non sequitur, at worst it demonstrates more confusion on your part.