What, exactly, is "safe" about TypeScript other than type safety?

TypeScript is just a language anyway. It's the runtime that needs to be contained. In that sense it's no different from any other interpreter or runtime, whether it be Go, Python, Java, or any shell.

In my view this really is best managed by the OS kernel, as the ultimate responsibility for process isolation belongs to it. Relying on userspace solutions to enforce restrictions only gets you so far.

Ah I forgot to add an /s

I agree on all counts and that this project is silly on the face of it.

My comment was more that there is a massive cohort of devs who have never done sysadmin and know nothing of prior art in the space. Typescript "feels" safe and familiar and the right way to accomplish their goals, regardless of if it actually is.