@groak The engine is made using svelte (a web framework), and vite (bundler/dev server) with a plugin that outputs everything as a single html file.
and yes, people can share the remixes! The engine has an export button for that (which also outputs an http file, which also includes the engine :D).
I have not figured the legal side of that though (the right open source license, what that means for remixes, etc.)