Comment by Animats

1. Nothing. Someone was writing a QNX-type kernel in Rust. What happened to that? There's L4, but it's too low-level. It's more of a hypervisor. People usually run another OS, usually a stripped-down Linux, on top of L4. QNX offers a POSIX API, so you can run applications directly.

2. C++. Here's the source code. [1]

3. No.

[1] https://github.com/John-Nagle/Overbot/