PHP-Nuke is a web based CMS (content management system) based on PHP and MySQL. All versions before PHP-Nuke 7.5 were (and still are) considered as free software, but as of version 7.5 a $10 fee is required. PHP-Nuke requires a web server with PHP support (Like Apache HTTP server) and a SQL server (MySQL, mSQL, PostgreSQL, ODBC, ADABAS, Sybase or InterBase, I recommend MySQL). Unfortunately, PHP-Nuke is riddled with security holes that the author didn't fix and users have to rely on unofficial patches. PHP-Nuke has been forked by a number of different people for many different reasons (for more info on those click here).