I think the semantics are important. Here’s another way of asking. Who owns the copyright today? Did you assign (sell) the right (has there been a change of ownership?) or did you merely grant a license and you still own the copyright?
Your language of “granting an exclusive perpetual right” sounds like you have not assigned (sold) the underlying entity. If you still own it, it still sounds like passive income to me regardless of how your payment gets structured or whether the license you granted is exclusive or not.
