osCommerce is an e-commerce and online store-management software program. It can be used on any web server that has PHP and MySQL installed. It is available as free software under the GNU General Public License.

Zen Cart branched from osCommerce as a separate project. Beyond some aesthetic changes, the major differences between the two systems come from Zen Cart’s architectural changes(e.g. a template system) and additional included features in the core. Among the modules already included