What software is Cloudflare DNS built on?

I think I can answer this, GitHub - cloudflare/dns: Clone of https://github.com/miekg/dns, but I wonder if Cloudflare still uses this software? It hasn’t been updated in years, so I imagine that it’s been cut off to the public. My best guess is that Cloudflare still uses it, but it’s even more heavily modified and integrated even more with Cloudflare’s current infrastructure and other software.