But look at the first sentence, Christoph.
Me and my brother made a rock version of one of the apple loops
Th OP wants to sell a new version of the loop as loop - and that seems to be problematic to me. Using the loops for something different is fime, but modifying it and selling it as a new loop? That may depend on the amount of change; how much modification will be necessary to make it a new loop?
Adjust the tempo? The volume? The rhythm? That is why I said, "ask your lawyer"; it does not seem to be as simple as using the loop for a different kind of project.
Or do you read the OP's intentions differently?