The core script runner to control any server which has Virtualmin and Phusion Passenger boot together.
This service is used to control a server booted with DOM Cloud Instance. It's actually installed for each DOM Cloud servers.
To understand DOM Cloud servers architecture, read it on DOM Cloud docs.
To setup a VM from stratch and set up this service in that VM, see Self hosting. You'll see that this service is need to run as a Systemd service.