IIRC, the Oracle guys came to Mozilla to give a talk about this. When Mozilla folks asked if it was open source, which at the time, the answer was "no." That response was met with a bunch of blank looks from both parties. Heh. At least, I think it was Graal. They were showing some VM running Ruby.
And yes, it was probably Graal. There's an accompanying language JIT construction toolkit called Truffle, and they already have implementations for Java, Python, JavaScript, Ruby and R.