From Joomla! Documentation
Portal:DevelopersRevision as of 21:09, 25 September 2013 by Tom Hutchison
The development of Joomla! itself is carried out by the Development Working Group and third party developers. This page is a starting point for developers interested in the development of components, modules, plugins and templates.
For more about core Joomla! development, how to contribute and becoming more involved with the core code, you should go to Joomla! Code Contributors