At the bottom of the page:

>Produced using pandoc and panflute with templates derived from gitbook and bookdown.

http://pandoc.org/

http://scorreia.com/software/panflute/

https://www.gitbook.com/

https://bookdown.org/

Yes I use a custom pandoc filter that transforms the markdown to both latex and html (using the bookdown/githook template).

At the moment the code is rather messy and somewhat tied to my windows setup , but eventually I plan to open source it as well.