osCommerce is the leading Open Source online shop e-commerce solution that is powered by a dedicated, strong, and ever growing community, and is released under the GNU General Public License.
2. Zen Cart
Zen Cart truly is the art of e-commerce; free, user-friendly, open source shopping cart software.
Magento is a robust e-commerce software application designed to be simple to customize.
A free shopping cart system. OpenCart is an open source PHP-based online e-commerce solution.
PrestaShop is a professional e-Commerce shopping cart software that you can download and use for free.