If you are confused on how to start developing for PS2, see the getting started section on the ps2dev main page.
This git repository contains various numbers of ports working with the current ps2sdk. It is not intended to be a releasable package.
Most of the ports contain specific changes to make them work for the ps2sdk, however, there are some ports included as a git clone that are being compiled using original source code, just adding the specific PS2 flags (using cmake).
Easy for everyone, just type
make
Links for discussion and chat are available here.