We use the OSS release of mDNSresponder fairly extensively and have patched it to fix some issues.
I was curious if Apple accepted such contributions upstream, or provided a way to communicate the changes for potential inclusion in future patches, as maintaining a fork isn't ideal for both parties.
It seems that PRs on the GH repo are not always reviewed, but there is some evidence that they are looked at. We realise that POSIX implementation for mDNSResponder might not be a priority for Apple, but curious if there's a process for contributions from industry?