The download for the code that is the starting point of the tutorial is here: http://www.oracle.com/technetwork/middleware/ias/order-jsf-jpa-tutorial-130794.zip
You can download a complete version of the application from here: http://www.oracle.com/technetwork/topics/order-jsf-jpa-example-128127.zip
The link "Understanding the Tutorial Source Files" is a dead link.
Note that there is an older version of the tutorial here: http://www.oracle.com/technetwork/middleware/ias/jsf-jpa-tutorial-095959.html
There is a blog post about setting up and running the order-jsf-jpa-example-128127 version of the application on PostgreSQL here: http://surfacedetail.blogspot.com/2015/04/how-to-fix-and-run-broken-eclipselink.html