What's the relationship between our Phabricator instance and upstream Phabricator?

I was curious about making user experience improvements to our Phabricator instance, but I’m not sure where the code is.

https://llvm.org/docs/Phabricator.html#status calls our instance a “derivative of an existing open source project,” presumably meaning we’re running some kind of fork of the official Phabricator. It links to the GitHub repository https://github.com/r4nt/llvm-reviews/, but that repository hasn’t been touched in 5 years. Is that actually what we’re deploying?

That repo just has the equivalent of dockerfiles to set up a machine should the current one die.

The deployed repo is https://github.com/r4nt/phabricator/tree/llvm-production