Hey. Great you are taking care of Latin Learners. As a Librarian, I think I can definitely answer:
You cannot share copyrighted Material directly. That is just how it is.
However, if the content is copyrighted but free, you can create a external lesson. That usually works because the user has to import it himself.
The best part is that you can still modify how the lesson is in terms of macrons etc.
Audio however is not automatically imported so if you want to provide users with audio in external lessons, they’ll have to be at least YouTube audio or something along those lines.
I hope that helped.