Earlier quoted context omitted.
There are mainly three reasons here: 1. We changed the source code too much that we are not able to merge it back to RocksDB easily (This project started at 2016 as an close-source project) 2. We have different road path with RocksDB (e.g. We will remove a lot of un-used code to make TerarkDB much more light-weight than current version in the future) 3. We have lots of third-party partners (e.g. Intel, on Opatane SSD…
3) is not in line with an open source philosophy. EDIT: Detrimental to the original. Eg. Amazon forking and selling MongoDB.
Are they giving back the source? And letting Mongo merge their changes if they wish?
Because that's what open source is all about.