Asterisk
Easy to use but advanced IP PBX system, VoIP gateway and conference server.
Jitsi Video Bridge
WebRTC compatible Selective Forwarding Unit (SFU) that allows for multiuser video communication.
Kamailio
Modular SIP server (registrar/proxy/router/etc).
Zim
Graphical text editor used to maintain a collection of wiki pages.
ZNC
Advanced IRC bouncer.
µStreamer
Lightweight and very quick server to stream MJPEG video from any V4L2 device to the net.
Dovecot
IMAP and POP3 server written primarily with security in mind.
WeeWX
Open source software for your weather station.
Xandikos
Open source CardDAV and CalDAV server with minimal administrative overhead, backed by a Git repository.
OpenSMTPD
Secure SMTP server implementation from the OpenBSD project.
ngircd
Portable and lightweight Internet Relay Chat server for small or private networks.
Red Eclipse 2
Arena first-person shooter similar to Unreal Tournament.
RSS2EMail
Fetches RSS/Atom-feeds and pushes new content to any email-receiver, supports OPML.
Supysonic
Python implementation of the Subsonic server API.
cmyflix
Minimalist Plex/Jellyfin alternative to stream video.
DAViCal
Server for calendar sharing (CalDAV) that uses a PostgreSQL database as a data store.
0 A.D.
Cross-platform real-time strategy game of ancient warfare.
Courier MTA
Fast, scalable, enterprise mail/groupware server providing ESMTP, IMAP, POP3, webmail, mailing list, basic…
Deluge
Lightweight, cross-platform BitTorrent client.
Exim
Message transfer agent (MTA) developed at the University of Cambridge.
FreedomBox
Community project to develop, design and promote personal servers running free software for private, person…
g3proxy
Forward proxy server supporting proxy chaining, protocol inspection, MITM Interception, ICAP adaptation and…
OpenSSH SFTP server
Secure File Transfer Program.
Postfix
Fast, easy to administer, and secure Sendmail replacement.