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).
PHP is a general-purpose scripting language used for web development.
vBulletin is tool that is used to create and manage online forums or discussion boards. It is written in PHP and uses a MySQL database server.
YUI is a JavaScript and CSS library with more than 30 unique components including low-level DOM utilities and high-level user-interface widgets.