From the Mozilla Blog:
“Popcorn allows web filmmakers to amp up interactivity around their movies, harnessing the web to expand their creations in new ways. Popcorn uses Javascript to link real-time social media, news feeds, data visualizations, and other context directly to online video, pulling the web into the action in real time. The result is a new form of cinema that works more like the web itself: interactive, social, and rich with real-time context and possibilities that continue to evolve long after filming wraps.”
More info on Mozilla Popcorn, Popcorn.js and Popcorn Maker at http://mozillapopcorn.org/.