This github repository neither hosts nor provide cdo sources, it's meant to host (unofficial) convenience files for Fedora and CentOs rpm packaging and feeding che copr repo: https://copr.fedorainfracloud.org/coprs/simc/stable/
For cdo source see: https://code.mpimet.mpg.de/projects/cdo/files
For information about cdo see: https://code.mpimet.mpg.de/projects/cdo/wiki
For CentOS and Fedora, rpm packages are hosted in a copr repo: https://copr.fedorainfracloud.org/coprs/simc/stable/