What is OpenRC?
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 the Gentoo Portage Tree. OpenRC, however, is not exclusively used by Gentoo Linux and can be used on different Linux and BSD systems.
Comments and Reviews
Said about OpenRC as an alternative
There is a long list of technical arguments for why OpenRC is better than systemd. Popularity wise systemd seems to win these days. But as we've seen over centuries popularity served us wrong many times. Even Upstart was better, pretty bad it faded away.