What does it solve?
Doesn't this exist already?
It does, but the alternatives are hard to use and they require the files you want to load to comply with different specifications like AMD or CJS.
Specifications are super nice, but if you don't have that and just want to lazy load some scripts, this is probably what you want.
What does it do?
Easily lazy load scripts when you need them or load them when the browser is idle.
Unbox keeps track of the scripts you've already loaded, so it enables you to create SPA's and other cool stuff.
Copy the whole source from Github.