The main responsibilty of the development working group is taking care of the development of the Joomla! application framework and the Joomla! Content Management System (CMS). Beside the development of the Joomla! codebase the development working group defines the Joomla! roadmap strategy, creating (architectural) designs for major and minor versions and of course take care of bug- and security fixes in maintenance versions.
The development working group holds two teams: the Development Team and the so called Bug Squad. The teams have separate responsibilities, but together they form the development force from the Joomla! project.