[amaranth]

C99 ensures it can be used with basically every other language and can be compiled for almost every platform. Bindings on top of that for other languages would be nice but can be provided by the community too. If it was C++, Rust, Nim, etc you'd have to write it in a way that allows exposing a C API anyway so the only advantage would be for people creating an implementation of the API getting to use a better language internally.

[pjmlp]

That can be achieved with an IDL that isn't unsafe by default and the cause of endless security bugs.

Then everyone can generate whatever bindings they feel like in an automated way.