Online conferencing
Exploring alternatives, particularly open source, for conferancing
Voice
Mumble
mumble is open source audio conferencing -
Video
Big Blue Button
BigBlueButton is an open source web conferencing system built on over fourteen open source components to create an integrated solution that runs on mac, unix, or PC computers
Jitsi
Secure video calls, conferencing, chat, desktop sharing, file transfer, support for your favorite OS, and IM network. All this, and more, in Jitsi - the most complete and advanced open source communicator.
See also
Web RTC
Web RTC is a standard protocol for encrypted video communication whose API is implemented in many open source browsers, such as Mozilla Firefox. There's a few open source software products that utilize Web RTC without requiring the installation of software other than the web browser (no addons needed). Many WebRTC-backed websites utilize proprietary software. Here's some that don't:
Jitsi Meet
Scalable website whose [sourcecode|https://github.com/jitsi/jitsi-meet] can be downloaded to run on your own apache webserver. Utilizes Jitsi Videobridge with SFU for scaleability