Wikipedia
ImpressPages
ImpressPages is an open-source PHP framework with built-in content editor. Features include MVC engine, inline editing and drag&drop interface. It is distributed under the GNU GPL v.3.0 and MIT licences.
The first stable version of ImpressPages came out in 2009. As of April 2014, version 4.0 has been released marking the shift from CMS to a PHP framework.