RocketChat - The ultimate open source web chat platform

•    Coffeescript

Rocket.Chat is a Web Chat Server, developed in JavaScript, using the Meteor fullstack framework. It is a great solution for communities and companies wanting to privately host their own chat service or for developers looking forward to build and evolve their own chat platforms. Its features include File sharing, Video conferencing, Screen sharing, Live chat, Link preview and lot more.

Bigbluebutton - Open Source Web Conferencing

•    Scala

BigBlueButton is an open source web conferencing system for distance education. It supports sharing of slides (PDF and any document readable by OpenOffice), webcams, whiteboard, chat, voice over IP (using FreeSWITCH), and presenter's desktop. It can record and playback sessions (slides, audio, and chat), runs on Mac, Unix, and PC computers, and is supported by a community of developers that care about good design and a streamlined user experience.

dimdim - Web Meeting

•    Java

Dimdim is an open source web meeting product with features like Application, Desktop and Presentation sharing with A/V streaming and chat. No attendee installation - all features are available through a web browser. Dimdim can be integrated with Moodle.

Jitsi - Video Calls and Chat

•    Java

Jitsi provides Secure Video calls, Conferencing, Chat, Desktop sharing, Instant Messaging, File transfer support for your favorite OS and IM network. Jitsi lets you connect to Facebook, GoogleTalk, XMPP, Windows Live, Yahoo!, AIM, and ICQ so that you can chat to all your friends in the simplest possible way. It supports IPv6, Secure calls with zRTP, Call history, Call hold etc.

WebHuddle - Simple Web Conferencing

•    Java

WebHuddle overcomes many of the common challenges faced by other virtual meeting applications on the market -- such as high-price to entry, compromised network security, large client downloads, and unreliability -- resulting in a frustrated IT department and less than satisfactory business results.

Sunrise - Open Video Conference Solution based on HTML5 WebRTC

•    PHP

Sunrise is an open video conference solution based on HTML5 WebRTC. You can use this software to talk with your friends, to have online meetings in your company, or to provide enhanced customer service, etc. Enjoy the next generation of the Web with Sunrise VC.

Kopano - Collaboration made easy

•    C++

Kopano Core provides the foundation for groupware messaging enabling clients such as Kopano WebApp, Kopano DeskApp, mobile and sync clients. With its modular architecture, Kopano Core enables the possibility for a variety of setup scenarios, scalable from a very low-powered system to a multi-datacenter setup providing messaging capabilities to tens of thousands of users.

FarSight

•    C

Audio/Video Conference software for Instant Messengers. It aims to provide Audio/Video conferencing for as many Instant Messengers as possible through a modular design.

jitsi-meet - Jitsi Meet - Secure, Simple and Scalable Video Conferences that you use as a standalone app or embed in your web application

•    Javascript

Jitsi Meet is an open-source (Apache) WebRTC JavaScript application that uses Jitsi Videobridge to provide high quality, secure and scalable video conferences. You can see Jitsi Meet in action here at the session #482 of the VoIP Users Conference. The Jitsi Meet client runs in your browser, without the need for installing anything on your computer. You can also try it out yourself at https://meet.jit.si .

Riot - Messaging and Colloboration made easy

•    Javascript

Riot is built on top of Matrix. Matrix is an open network for secure, decentralized communication delivering a community of users,bridged networks, integrated bots and applications plus full end-to-end encryption. Riot allows teams to communicate across a wide range of collaboration apps. If some team members use Riot while others use IRC, Slack or Gitter, Riot will allow these team members to seamlessly work together. Riot offers the richest network of communication bridges.

Blink - easy to use SIP client

•    Python

Blink is a GUI for Mac, Windows and Linux built on top of SIP SIMPLE client SDK. It uses SIP (Session Initiated Protocol) for VOIP and Instant Messaging. It supports Multi-party conferencing, Missed Calls, Dialing out SIP addresses and telephone numbers. Currently File Transfer and Desktop sharing is supported only in Mac.

Tox - The future of online communications.

•    C

With the rise of government surveillance programs, Tox, a FOSS initiative, aims to be an easy to use, all-in-one communication platform that ensures full privacy and secure message delivery. Tox must use UDP simply because hole punching with TCP is not as reliable. However, Tox does use TCP relays as a fallback if it encounters a firewall that prevents UDP hole punching.

Matrix - Decentralized group communication

•    Python

Matrix is an open standard for decentralised communication, providing simple HTTP APIs and open source reference implementations for securely distributing and persisting JSON over an open federation of servers. It can be used for Decentralised Group Chat, WebRTC signalling, Internet of Things, VOIP etc.

Hublin - An easy and free video conference service

•    Javascript

Hubl.in is a free and open source video conference solution built with love and designed with ethics in mind. It's the best way to initiate a communication anywhere with anybody and brings real time conversation to the next level. Hubl.in allows free communication without additional plugins.

indico - Indico - A complete event management system

•    Python

Indico is a general-purpose event management web-based solution. It includes a full-blown conference organization workflow as well as tools for meeting management and room booking. It provides as well integration with video-conferencing solutions. Indico is free software, licensed under terms of the GNU General Public License (GPL) v3. It is currently in production at CERN, as well as in many other scientific institutions around the world.

MSNSharp Application with Video Conferencing Feature

In MSN World, users don’t communicate directly each other.I examined P2P open source video/audio conference systems . After researching, I found VideoNet application suitable and modified VideoNet and adapted to MSNPSharp. I also used Mimic Codec for Video

bigbluebutton - Complete open source web conferencing system.

•    Java

BigBlueButton is an open source web conferencing system. BigBlueButton supports real-time sharing of audio, video, slides (with whiteboard controls), chat, and the screen. Instructors can engage remote students with polling, emojis, and breakout rooms. BigBlueButton can record and playback all content shared in a session.

SipXcom - Unified Communications System

•    C++

sipXcom open source unified communications software is the standard for enterprise voice solutions. Voice, chat, IVR, presence and more in one application. It provides complete enterprise grade telephony, unified messaging, Instant messaging, audio conferencing, and many other features. sipXcom can be run along side your existing Cisco, Avaya, Mitel, Shortel or other PBX while you migrate users to the sipXcom system.

CIM3

•    C

Provide a secure and centrally managed Business Instant Messaging Solution (server/client), including Chat, Voice / Video Conferencing, File Transfer, Emoticons, Dictionary and Tools add-in function etc.

SFLphone - Softphone for Linux

•    C++

SFLphone is a softphone for Linux. It is SIP compatible and supports Multi-way conferencing, Peer to peer calls, Video calls, Instant Messaging, Multi-line, Call transfer, Call hold, Call recording and lot more. It encrypts voice using SRTP protocol.