It’s worth noting that I created a separate folder for the german style files and first copied the original OSM mapnik style files and ontop the mapnik-german style files.

    cp -R mapnik mapnik.de
    cp -R mapnik-german/* mapnik-de/
    # remove subversion files
    find  ./mapnik-de/ -type d -iname ".svn" -exec rm -r -f {} \;