PostNuke is a free, open source content management system (a 'nuke') forked 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. They felt the only way this could be done was to develop their own fork of the PHP-Nuke code. PostNuke is now a separate project sharing very little code (if any) with the original project.