The author wrote this on reddit:
> What does "Rust-first" mean here? It means not only that both the (micro) kernel and the drivers are implemented in Rust, but also that Rust is the first (and only, at the moment) language that userspace programs can be written in.
> Although technically one can reverse-engineer the Rust-based ABI and the provided Rust toolchain to write apps for Motor OS in e.g. C, that is some work. But standard Rust programs (using standard Rust library, without FFI) will just compile and run - see e.g. https://github.com/moturus/motor-os/tree/main/src/bin/httpd.
> This Rust-first approach is rather unique, as e.g. Redox uses relibc and C-based kernel ABI as the glue...
https://old.reddit.com/r/rust/comments/190znk5/mot%C5%ABrus_...