It's analogous to asm.js, the precursor to WebAssembly, which was written in js, in that it ran virtual machines in pure js, which is a huge win in portability. The mquickjs readme explains it in a much lower level way than the quickjs readme. There's also more emphasis on the bytecode. In a way it's like a tiny WebAssembly plus garbage collection extension vm that can run compile to js languages, going beyond that and compiling them to bytecode. The overhead of porting it to a dynamic language wouldn't always be that bad depending on the use case. Its memory savings could be maintained.