From the site:

GroundWork Monitor Community Edition provides a essential IT monitoring solution that enables you to maintain network visibility and control.

This is a single server deployment that leverages the strengths of 15 other open source projects such as Nagios, rrdtool and nmap. It combines the results of these projects in to a system that evaluates the status, events and performance of monitored devices and presents these results in an easy to understand web application.

This open source project distributed on sourceforge.net is available under the GNU Public License (GPL v2). It is ideal for operations who already have deployed one or more open source monitoring projects and need to expand its capability.