Video SDK from Zoom - Build fully customizable video-based apps
Asterisk - An open source telephony switching and private branch exchange service for Linux.
Amazon Chime - Online meetings and video conferencing
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.
100ms Live - Video and Live Streaming infra for a video-first world
FusionPBX - FusionPBX is an open source FreeSWITCH GUI.