Zabbix
4.0 mai na 5 na kalokalo (yavutaki ena 1 railesuvi)
Zabbix is an open-source software tool to monitor IT infrastructure such as networks, servers, virtual machines, and cloud services. Zabbix collects and displays basic metrics.
The software itself seems to be trade-free. The website though offers some consulting which one would need to pay for: https://www.zabbix.com/consulting – therefore 4/5 blocks.