It's not really a binding. It doesn't link to anything in systemd, it's just aware of the convention used by systemd to pass the file descriptors into the process. The actual code being executed from that repository is around 60 lines, I guess:
I just used that rather than writing it myself because it felt like it didn't add much to the story. Also the code was actually written on macOS, it still runs fine without systemd.
Edit: I'd be quite interested to see if passing file descriptors in this way would be a goal in, for example, the proposed Alpine service manager. A quick scan of the proposal didn't show me anything obvious, but I'll go and read it in more detail.
https://github.com/coreos/go-systemd/blob/main/activation/li...
I just used that rather than writing it myself because it felt like it didn't add much to the story. Also the code was actually written on macOS, it still runs fine without systemd.
Edit: I'd be quite interested to see if passing file descriptors in this way would be a goal in, for example, the proposed Alpine service manager. A quick scan of the proposal didn't show me anything obvious, but I'll go and read it in more detail.