EvenCart is no longer an Open Source product. However there are public forks that you can use under the license terms they were forked. The following are available forks.
You can use the source code from the above forks under EvenCart Licenses of your choice.
Note: EVEN IF YOU ARE USING ANY OLD FORK (WHEN EVENCART WAS OPEN SOURCE), YOU STILL NEED TO COMPLY WITH ONE OF THE EvenCart Available Licenses.