Could you clarify your question? The fuchsia subdir contains various user space components of the OS, like a network stack, bluetooth, graphics drivers, etc. Also some tools and test code. Rust is used in most of the components I looked at.

Edited my comment. Didn’t notice that vendored got spelling corrected to censored :(

Ok now your question makes sense, thanks.

> does the src directory include any vendored software for the other languages? Or is that also only fuchsia code?

It doesn't contain vendored software. The third_party dir is responsible for that, at least for Rust and Go. The C libraries used are in separate repos I think.