If you want to test DIRACOS in a DIRAC installation, it is enough to do the following:
https://raw.githubusercontent.com/DIRACGrid/DIRAC/integration/Core/scripts/dirac-install.py
chmod +x dirac-install.py
./dirac-install.py -r v6r20 --dirac-os --dirac-os-version=0.0.5
If you want to install it together with your extension, you will most probably have to copy the diracos tar files from http://lhcbproject.web.cern.ch/lhcbproject/dist/Dirac_project/installSource/ to your own baseURL