ShareX - ShareX is a free and open source program that lets you capture or record any area of your screen...
Asterisk - An open source telephony switching and private branch exchange service for Linux.
Greenshot - Greenshot is a free and open source screenshot tool that allows annotation and highlighting using the built-in image editor.
FreeSWITCH - FreeSWITCH is an open-source media application designed to support popular protools such as SIP and WebRTC and provides a platform to develop voice and video applications.
LightShot - The fastest way to take a customizable screenshot.
freepbx - FreePBX is a web-based open source GUI that controls and manages Asterisk (PBX).