The point is that Emile is 50 lines of code and can be wrapped up for any purpose in about 2 minutes (export to some object).

Dustin wanted a different API to call upon, so he had to change some stuff, again relatively easy, because it basically fits on a screen in a text editor.

Let's not forget, all of this is open source, and it's meant for adaptation, forking and to be built upon. (Note that Emile was very much a proof-of-concept, with no emphasis on beatuiful, reusable code; it was written as a teaching tool for a talk on CSS animation I gave two years ago at Fronteers.)