OK, I’m down the rabbit hole now 
There appears to be at least 1 official repo and two forks.
drolbr’s original repo, used by the .de and .fr instances, that is way behind both other forks
mmd-osm’s fork that has several performance improvements but with no commit in the last 2 years and diverged from source
b1tw153’s fork that is just an up to date version of drolbr’s, without the improvements of mmd’s, but with other improvements.