KillingSpark

I'm Just going to plug myself here:

https://github.com/KillingSpark/rustysd

Rustysd is a reimplantation of the core features of the systemd service manager with a deliberate focus on less features so it can work on more platforms (e.g. BSD)

It's been a while since I actively progressed on the project but it works and would probably be a good starting point for anyone wanting to do further work in this direction.