Yes, I can understand that a lot of people will not understand "cc-by-sa 4.0" by itself so it's a good idea to add an explanation. The one does not exclude the other.
I suggest a change like this in the German text: "Die Vorteile gegenüber Closed Source Software (="verschlossene" Software)" -> "Die Vorteile gegenüber unfreie oder proprietäre Software"
