It would be simple to get anyone into OS development. The only easier language I can find to teach someone is Python, and that doesn't have such an easily portable runtime.

JavaScript is great because you can learn it in the afternoon and master it in a few years and has a nice subset of lisp-like features.

It would be a toy to prototype in. Easy to use, and easy to modify. Nothing serious.

For me it'd be a great way to learn about OS with something I'm already really familiar with, and also something that I can easily hack on. I.e. Similar reasons why I much more prefer stumpwn to ratpoison.