PostNuke was a free, open source content management system (a 'nuke') forke from PHP-Nuke, released under the GNU General Public License. The PostNuke project was started because some PHP-Nuke users believed there should be a more open development environment. The users felt the only way this could be done was to develop their own fork of the PHP-Nuke code. PostNuke has grown beyond PHP-Nuke and become a project standing on its own merits. Like XOOPS, PostNuke's code is object oriented and fully modular.