What does it do?

Serves DNS zone files over Multicast DNS.

How does it do it?

A UDP server built atop CoreNetworking.

What does it even meme?

Allows you to inject DNS responses into the Bonjour Multicast DNS server on your local network using a zone file.

Configuration is handled by the DNS_ZONE_FILE environment variable. This should be the path to a single zone file or to a directory of zone files.

The server can then be queried over multicast using dns-sd, see x-man-page://dns-sd.

The shared scheme included in the project serves the db.example.local. zone which includes A and AAAA records for the example.local. host, these can be queried using dns-sd -G v4v6 example.local..

If you actually want to run this (why would you want to run this?) I'd recommend using a launchd job, see x-man-page://launchd.plist.

Who even writes a DNS server?

Who doesn’t write a DNS server.