It's not very difficult at all to call Rust libraries from other languages by using #[no_std] and exposing a C API. You're correct in that this does currently dispose of the entire standard library, which is rather unfortunate. We're still exploring options for partitioning the stdlib into levels such that you can lose just the stuff that needs a runtime (heap allocation, concurrency) without losing all the other goodies (overloaded operators, iterators, etc.)