Cost / License
- Free
- Open Source (Apache-2.0)
Platforms
- Linux
OpenRC is a dependency-based init system that works with the system provided init program, normally /sbin/init. It is not a replacement for /sbin/init. OpenRC is 100% compatible with Gentoo init scripts, which means you can probably find one for the daemons you want to start in...
systemd is a suite of basic building blocks for a Linux system. It provides a system and service manager that runs as PID 1 and starts the rest of the system.

runit is a cross-platform Unix init scheme with service supervision, a replacement for sysvinit, and other init schemes. It runs on GNU/Linux, *BSD, MacOSX, Solaris, and can easily be adapted to other Unix operating systems.
The Sysvinit package contains programs for controlling the startup, running, and shutdown of the system.
a free system array created by Apple inc. For BSD - including macOS as macOS is based on the Darwin kernel of BSD
Supervisor is a client/server system that allows its users to monitor and control a number of processes on UNIX-like operating systems.



procd is a process and system init service for OpenWRT. It's less resource intensive as it's intended for embedded devices, works with busybox and uClib, hotplug2, libubox and ubus. It watches configuration files to start or restart services and init scripts