MN Viewer (Mobile Network Viewer) is a lightweight framework designed for system administrators who would like to be able to monitor many aspects of their network from their mobile phone. It allows for very simple expansion using simple PHP plugins. It is designed to integrate with other monitoring tools such as Cacti.
LibreNMS is an autodiscovering PHP/MySQL-based network monitoring system forked from Observium. It aims to be easy to use and painless to deploy, and to support monitoring of a wide range of devices. Observium's license changed to a modified QPL license in May 2012, then was split into free and commercial versions. The aim of LibreNMS is to continue to create a usable NMS, but with a community focus and GPL licensing.