Author here. Thanks for the interest in active markdown! I’ve given the project a proper home on the web:
http://activemarkdown.org. It has more recent controls that don’t use jQuery UI. The controls are Tangle-inspired, but not actually using the Tangle library.
Regarding usecases, Brett Victor’s article
http://worrydream.com/ExplorableExplanations/ does a much better job at explaining the idea of reactive documents than I could. There are some great examples on it. He even asks “Can it be almost as easy as writing static text?” at the bottom, which, while not the inspiration for this project, is exactly the goal.
That gets into tooling. Tangle requires authoring a small webapp, using its library and helpers. That’s not particularly challenging for many, but it’s still a significant barrier. Also, there’s no “fallback” format, whereas markdown is just plain text. The intent with active markdown is to have plain text that can turn into interactive representations, while only requiring the `activemd` command. And I’d like to make even that not necessary with an online converter.
PS Trudi at Concord deserves a lot of credit for being a great Comp Sci teacher! She played a big part in developing my interest in programming.