No, these files don't go in the project itself, they contain instructions and resources for the Arch Build System
to download, build and install it. They can be used as they are or published in the AUR for wider/easier access,
The project folder you've linked looks to me like an attempt to script that process.
(I'm assuming these scripts don't work correctly/without effort, because otherwise why wouldn't ngld have used them?)
Since the PKGBUILD is essentially a "recipe" to make knossos, somewhat experienced users of other distros could
probably follow it by hand, if no built release is made.