Popcorn.js is a javascript library, so someone who knows Javascript can do all the things shown in the demo using the library. Takethislollipop is running on popcorn.js. The neat thing here is that Mozilla is creating software for people that are NOT devs, so that they too can be creative in bringing dynamic data into a video, while at the same time learning about some of the open technologies that power the digital world.
If you want to, and you have that few weeks, you can contribute: https://wiki.mozilla.org/PopcornMaker/QA