I contacted the developers of WP courseware.   I want to know from them if it would be possible to register multiple users under one email.   Unfortunately, this is not going to be possible.

Here is their reply:

Unfortunately, this isn’t possible since WordPress requires unique emails when registering. Since WP Courseware piggy backs off of the WordPress user database, it isn’t possible to have someone enroll with the same address. Multiple email addresses will need to be created. That said, if the students don’t care about receiving email communications from WP Courseware, you can always create “bogus email addresses”, however, if they want to get their progress, grades, and certificate notifications, then they will certainly need unique email addresses.

I’m sorry, guys.   I tried.