Software

Flat-forum bulletin board software solution that can be used to stay in touch with a group of people or can power your entire website. ([Source Code](https://github.com/phpbb/phpbb))

Ethical photo sharing platform, powered by ActivityPub federation (alternative to Instagram). ([Source Code](https://github.com/pixelfed/pixelfed))

Federated microblogging server, Mastodon, GNU social, & ActivityPub compatible. ([Source Code](https://git.pleroma.social/pleroma/pleroma))

Q&A-based community knowledge-sharing software. ([Source Code](https://github.com/codidact/qpixel))

Lightweight and simple comment engine, which doesn't spy on users. It can be embedded into blogs, articles or any other place where readers add comments. ([Demo](https://remark42.com/demo/), [Source Code](https://github.com/umputun/remark42))

Stack Overflow in a JAR. An enterprise-ready Q&A platform with full-text search, SAML, LDAP integration and social login support. ([Demo](https://live.scoold.com), [Source Code](https://github.com/Erudika/scoold))

Free, professional grade software package that allows you to set up your own online community within minutes. ([Source Code](https://github.com/SimpleMachines/SMF))

Federated and decentralized profile builder and social network engine. ([Demo](https://socialhome.network/), [Source Code](https://github.com/jaywink/socialhome))

Create a community, where your users can suggest ideas and get questions answered. And have friendly open-ended discussions and chat (Slack/StackOverflow/Discourse/Reddit/Disqus hybrid). ([Demo](https://www.talkyard.io/forum/latest), [Source Code](https://github.com/debiki/talkyard))

Self-Hosted, Twitter™-like Decentralised micro-logging platform. No ads, no tracking, your content, your data. ([Source Code](https://git.mills.io/yarnsocial/yarn))

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. ([Source Code](https://github.com/bigbluebutton/bigbluebutton))

Video conferencing server that is easy to deploy and that requires moderate server resources. ([Source Code](https://github.com/jech/galene))

General-purpose, lightweight, minimalist WebRTC Server. ([Demo](https://janus.conf.meetecho.com/demos/), [Source Code](https://github.com/meetecho/janus-gateway))

WebRTC application that uses Jitsi Videobridge to provide high quality, scalable video conferences. ([Demo](https://meet.jit.si), [Source Code](https://github.com/jitsi/jitsi-meet))

WebRTC compatible Selective Forwarding Unit (SFU) that allows for multiuser video communication. ([Source Code](https://github.com/jitsi/jitsi-videobridge))

Real-time cam-2-cam video calls & screen sharing, end-to-end encrypted, to embed in any website with a simple iframe. ([Source Code](https://github.com/miroslavpejic85/mirotalkc2c))

Simple, secure, fast real-time video conferences up to 4k and 60fps, compatible with all browsers and platforms. ([Demo](https://p2p.mirotalk.com/newcall), [Source Code](https://github.com/miroslavpejic85/mirotalk))

Simple, secure, scalable real-time video conferences up to 4k, compatible with all browsers and platforms. ([Demo](https://sfu.mirotalk.com/newroom), [Source Code](https://github.com/miroslavpejic85/mirotalksfu))

Scalable and high performance web conferencing system. ([Demo](https://demo.plugnmeet.com/login.html), [Source Code](https://github.com/mynaparrot/plugNmeet-server))

XMPP instant messaging server. ([Source Code](https://github.com/processone/ejabberd))

Mobile messaging platform with a focus on performance and scalability. ([Source Code](https://github.com/esl/MongooseIM))

Real time collaboration (RTC) server. ([Source Code](https://github.com/igniterealtime/Openfire))

Feature-rich and easy to configure XMPP server. ([Source Code](https://hg.prosody.im/))

All-in-one Dockerized easy XMPP solution, including web admin and clients. ([Source Code](https://github.com/snikket-im/snikket-server), [Clients](https://snikket.org/app/))