Delta Chat is like Telegram or Whatsapp but without the tracking or central control. Delta Chat does not need your phone number. Uses the most massive and diverse open messaging system ever: the existing e-mail server network. Chat with anyone if you know their e-mail address, no need for them to install DeltaChat! All you need is a standard e-mail account. Full clients for multiple platforms available.
A Matrix server written in C++. Uses Boost, RocksDB, and Sodium for its back end. Currently implements all of the Matrix spec; implementing IRC is next.
Dendrite will be a Matrix server written in Go. Requires Kafka (if run as a cluster of microservices) or something called Naffka (an embedded in-process workalike) if run monolithically. Requires Postgres as its back end.
Epicyon is an AGPL licensed ActivityPub protocol compliant federated social network server suitable for hosting a small number of accounts on low power systems requiring minimal maintenance, such as single board computers. It's the ActivityPub equivalent of an email server, storing posts as human readable JSON on file, rather than in a database. It also uses only a small amount of RAM.
Python, HTML+CSS. Almost no JS is used.
Has pretty much all of the features you'd expect. Has a calendar feature for local users. Has bookmarking of specific posts.
Instant messaging server. Backend in pure Go (license GPL 3.0), client-side binding in lots of different languages. Also supports gRPC and HTTP(S)+Websockets. Supports persistent storage with a back-end database.
This is not XMPP, but I added the tag so it's easier to find later.
This is also a proof-of-concept web client: https://github.com/tinode/webapp/
Ethical and privacy-conscious alternatives for websites and apps.
A federated microblogging application written in node.js. Replaces Twitter. Implements ActivityPub so it's already part of the Fediverse.
A collective aimed at activists that uses only OSS software and federated or decentralized software. Offers services that you can request accounts on or set up your own server and federate with them.
3750 links, including 200 private