Currently it's set up to use Jekyll built into Github Pages. For local testing it requires Ruby.
This could be swapped to some completely different toolchain, like Sphinx (Python) or Metalworks (node.js) but requires that final HTML files are committed into repo.
https://help.github.com/articles/using-jekyll-with-pages/
In short:
- Install Ruby 2.x
- gem install bundler
- bundle install