I feel stupid. I did a search in the forum and was able to find someone with the same problem. The instruction to do this are also in the script itself.
You need to change this line:
// request login? true - show login and password boxes, false - password box only
define('USE_USERNAME', true);
to this:
// request login? true - show login and password boxes, false - password box only
define('USE_USERNAME', false);