Well RPython is just that: a restricted subset of Python (hence the name). Similarly, asm.js is a (small) subset of ECMAScript targeted at compile-to-js code g

Well RPython is just that: a restricted subset of Python (hence the name). Similarly, asm.js is a (small) subset of ECMAScript targeted at compile-to-js code generators. It's just about specifying what the subset contains, not inventing a new language.