TypeScript is great and everything, but Microsoft owns the standard and the single functioning checker, and haven't published a specification or even a grammar.
The TypeScript checker/compiler is Apache 2.0 licensed, so I'm not sure there's room to complain, unless you disagree with the direction they're taking the project:
Nobody disputes that TypeScript is open source, but there’s still a vast difference between a single open-source implementation and a specification that’s suitable for standardization. The implementation inevitably has bugs, and there needs to be a way to decide which bugs are actually “features” that other implementations will need to emulate.
To be clear, I am not bashing Microsoft here—just pointing out a reason that TypeScript can’t be declared “the next version of JavaScript”, which is the context of this thread.
https://github.com/microsoft/TypeScript/blob/main/LICENSE.tx...