This looks pretty interesting and I’ve not fully got my head into the details yet however I think you have possibly put this into the wrong category. The first thought I got from the first few paragraphs was this was looking like something in the realm of Lumen but taking inspiration from BEAM / Erlang rather than implementing it. It seems however it is a server side thing.
From the FAQ page:
What is Lunatic?
Lunatic is a universal runtime for fast, robust, and scalable server-side applications. It’s inspired by Erlang and can be used from any language that compiles to WebAssembly.
From what I can wrap my head around this seems to be an Erlang inspired web assembly runtime environment allowing people to run web assembly modules of some kind as something similar to processes. It claims to do many of the core things like isolation, own stack/heap, inter process messaging, pre-emptive scheduling, super light processes, big concurrency… but the processes themselves execute WASM and it seems like runtime features are surfaced through libraries. I think the idea is building backends from loads of tiny WASM things that live in and talk to each other on a BEAM like runtime layer.