OK but not from the creators of the languages themselves, I think?

The point remains though that it's the same situation. There's a free open source implementation and some companies that offer paid support.

Dotnet has commercial support from Microsoft. They are C# inventors.

(Also to needlessly quibble, technically James Gosling under Sun Micro-systems invented Java)

Pretty sure you can get support from Microsoft or other vendors for their C++ compilers.