Free server software

vsftpd (or very secure FTP daemon) is an FTP server for Unix-like systems, including Linux. It is the default FTP server in the Ubuntu, CentOS, Fedora, NimbleX, Slackware and RHEL Linux distributions. It is licensed under the GNU General Public License. It supports IPv6, TLS and FTPS (explicit since 2.0.0 and implicit since 2.1.0).

GNU MediaGoblin (also shortened to MediaGoblin or GMG) is a free, decentralized Web platform (server software) for hosting and sharing many forms of digital media. It strives to provide an extensible, federated, and freedom-respectful software alternative to major media publishing services such as Flickr, DeviantArt, and YouTube.

ProFTPD (short for Pro FTP daemon) is an FTP server. ProFTPD is Free and open-source software, compatible with Unix-like systems and Microsoft Windows (via Cygwin). Along with vsftpd and Pure-FTPd, ProFTPD is among the most popular FTP servers in Unix-like environments today. Compared to those, which focus e.g. on simplicity, speed or security, ProFTPD's primary design goal is to be a highly feature rich FTP server, exposing a large amount of configuration options to the user.

OpenSimulator is an open-source server platform originally launched in 2007 for hosting virtual worlds and metaverse environments. It is largely compatible with the virtual world Second Life but full compatibility is not a design goal.

Bitnami is a library of installers or software packages for web applications and software stacks as well as virtual appliances. Bitnami is sponsored by Bitrock, a company founded in 2003 in Seville, Spain by Daniel Lopez Ridruejo and Erica Brescia. Bitnami stacks are used for installing software on Linux, Windows, macOS and Solaris. VMware acquired Bitrock, along with its two largest properties, Bitnami and InstallBuilder, on May 15, 2019.

Pure-FTPd is a free (ISC license) FTP Server with a strong focus on software security. It can be compiled and run on a variety of Unix-like computer operating systems including Linux, OpenBSD, NetBSD, FreeBSD, DragonFly BSD, Solaris, Tru64, Darwin, Irix and HP-UX. It has also been ported to Android.

Kamailio, formerly OpenSER (and sharing some common history with SIP Express Router (SER)), is an SIP server licensed under the GPL-2.0-or-later license. It can be configured to act as a SIP registrar, proxy or redirect server, and features presence support, RADIUS/syslog accounting and authorization, XML-RPC and JSON-RPC-based remote control, SQL and NoSQL backends, IMS/VoLTE extensions and others.

lightweight DICOM server

free and open-source Shadowsocks deployment tool

open source project that provides pre-packaged server software appliances

H.323 gatekeeper implementation