You don't need anybody's permission to do this. Linux has a language-agnostic system call interface. Everything that happens on the computer is accomplished through that interface, and to use it all you need to do is put some values in specific registers and issue a special instruction. This isn't the domain of C; the JIT compiler could have a special system call generation feature. You could get rid of GNU and write your own user space in Lisp if you wanted to.