Apache is a free and open-source cross-platform web server software.
CentOS is a Linux distribution that provides a free, community-supported computing platform functionally compatible with its upstream source, Red Hat Enterprise Linux (RHEL).
HTTP Strict Transport Security (HSTS) informs browsers that the site should only be accessed using HTTPS.
Phabricator is a suite of web-based software development collaboration tools, including the Differential code review tool, the Diffusion repository browser, the Herald change monitoring tool, the Maniphest bug tracker and the Phriction wiki. Phabricator integrates with Git, Mercurial, and Subversion.
PHP is a general-purpose scripting language used for web development.