The GitHub repo is here; https://github.com/OvertureMaps/data -- Licenses look super permissive - I'm not that familiar with the state of Open Mapping but the GERS idea looks great too.
Curiously, two of the four layers use the ODbL.
Probably this data is reformatted OpenStreetMap data or derived from it (so is licensed as ODBL and requires attributing OpenStreetMap)