Jetlang doesn't offer lightweight-threads. It uses an event-driven processing of messages (like Akka), so fibers can't block and you can't do selective receives.
The JVM's GC isn't per actor (I know actors are called processes in Erlang, but let's keep the nomenclature consistent), but its GC is extremely advanced, and some implementations work on a per-thread basis. The ramifications are that we can't offer the same level of isolation as Erlang, at least not on HotSpot. An actor could theoretically produce a particular kind of garbage that will cause a GC pause to the entire system. But other than isolation, the JVM is very performant (much more than Beam), and handles concurrency extremely well.
I don't understand your last question (on load distribution).
Re: distribution, I just deleted this question from my comment. I had not payed attention to the item in "next steps" in your post which mentions Galaxy.
I'm excited to see how you guys go about trapping errors and such, as you mention in the "next steps."
You can do selective receives by creating and disposing channel subscriptions according to actor state. And a fiber can always spawn a conventional thread to block and publish a message when done.
The JVM's GC isn't per actor (I know actors are called processes in Erlang, but let's keep the nomenclature consistent), but its GC is extremely advanced, and some implementations work on a per-thread basis. The ramifications are that we can't offer the same level of isolation as Erlang, at least not on HotSpot. An actor could theoretically produce a particular kind of garbage that will cause a GC pause to the entire system. But other than isolation, the JVM is very performant (much more than Beam), and handles concurrency extremely well.
I don't understand your last question (on load distribution).