the SystemURL is used sometimes on internal redirects, it is setup on the initial install via install-ns, which also writes the default config file. When you change the host configuration (using different ip-address etc.) you have typically to change both, the config file and the SystemURL, and as well the "service" file. In general, the NaviServer config file allows to configure the listen on e.g. all IP addresses of your machine (see the first section of the naviserver config file).
Concerning running as a service: Depending on the version of linux, install-ns creates either a UpStart file (usage: status|start|stop oacs-5.9) and/or a systemd file (usage: systemctl status|start|stop oacs-5.9). running on older Ubuntus, you get upstart, some ubuntu versions support upstart and systemd (where the script generates both), redhat/fedora/centus use sytemd. When you change e.g. IP-addresses and/or ports, you have to update the service files in use as well (see the comments in the service files).
