Unless it's some real magic (please share if it is), I believe the best they can do is either spawn a node process from Ruby/PHP/Python, or use embedded v8 or similar interpreter. Which is not any different from running node "the normal way".

React is implemented in JS and uses JS to declare components, and it would be fun if there is some working JS-to-Python (-to-PHP/-to-Ruby) translator that is good enough to translate React code to run "natively".