I dislike CoffeeScript as much as the next guy, but the most complicated widget is 35 lines of CoffeeScript, most of which is pretty much identical to what the JS would be. There looks to be less than 100 lines of CoffeeScript outside of the widgets. If there's a project where I can overlook the use of CoffeeScript this is it...

Interestingly for me it's the reverse: using CoffeeScript lowers the barrier to entry :-)

I would not be surprised if spinning up on CoffeeScript was easier for beginners without real JavaScript experience.

It was much easier to get started to CoffeeScript for me, and learning it made me much more comfortable with writing JavaScript directly straight after.

yeah, probably. Dunno if it's a good thing, that people start with a transcompiled language...

That's just an implementation detail. CoffeeScript has syntax and semantics every bit as valid as JS's.

True story. JavaScript seems like a mix of C and Scheme CoffeeScript seems like a mix of Ruby and Python

You can still use plain old JavaScript if you want.