The kernel is composed of a number of modules, found in the *module/* directory. Which modules are included can be customised by changing the include statements in *module/init.lua*; copying it and customizing that is recommended, so you can *git pull* later without having to stash or reset your changes.
Documentation is generated as the system is built with build.sh; a set of markdown files will be placed into *doc/*, as well as an all-in-one *apidoc.md*. If pandoc is installed, an *apidoc.pdf* will also be generated.