This file explains all the directories of the source tree :

doc				documentation about the system
mnt				temporary folder for mounting disk images
src				source code
src/include		all includable headers to be used in userland
src/include/gc	Grapes Core (communication with the kernel) headers
src/include/gm	Grapes Modules headers
src/kernel		kernel source
src/library		source and linkable objects to be used by userland applications
src/modules		userland applications