I never did end up open sourcing it, but it is based on the old SteemDB repo with a few tweaks to make it for golos.
The problem with that codebase though is that it needs to be recreated, it's suffering from bloat and hitting walls with resource limitations. That's what this post was primarily all about and SteemDB suffers from the same problems.
My goal isn't to improve the code that already exists but instead create a new explorer codebase that scales much better. SteemDB (and shortly after, GolosDB) were some of my first projects in the blockchain space, so they aren't really built properly.