MacRuby doesn't run on an interpreter, it has several ways of running with JIT bytecode compiling as its default. The biggest hurdle for MacRuby is that it use

MacRuby doesn't run on an interpreter, it has several ways of running with JIT bytecode compiling as its default. The biggest hurdle for MacRuby is that it uses garbage collection, which isn't available on the iPhone OS. Applications will still need to be 'signed' to run on the iPhone.