Just came across this which could help you. Source: about 3 years ago

Reloading is nothing new under the sun for Lisp, I believe. For ML and adequate reload-ability, one might be hard pressed, but it's nothing new under the Sun (hint, hint). Maybe too on the nose, but one probably wants good inlining, and thus more "speculative" de/optimisation to preserve redefinition. Source: over 1 year ago

If they don't want Oracle's Java, why can't they use a subset of OpenJDK (licensing noob here)? Source: almost 2 years ago

Does this change affect https://openjdk.java.net/ too? Source: about 2 years ago

I think they use a circular queue of functions that is each executed for around 100 ms. I am guessing the system timer is used to generate an interrupt that pauses execution of the current function and starts executing the next function. Apple's Java code is probably closed source. I did find mention of an openjdk here: https://openjdk.java.net. I haven't looked at the source code yet. Source: about 2 years ago

What exactly is unsubstantiated here? Have you looked at OpenJDK's sources and/or licence and/or contributors? They're right here. And here's the project's homepage: https://openjdk.java.net. Source: about 2 years ago