Earlier quoted context omitted.
> I'm not aware of this principle. Where is it spelled out? Well, do CDs give you a license agreement that allows you to copy the data? I've never seen one. And it's nearly impossible to play a CD without that copying.
> And it's nearly impossible to play a CD without that copying. Exactly. It's how you are supposed to use the CD. That's not true for your example of a book on a webcam. You're supposed to read the book, not an image of the book. That's not the same thing as copying for "processing".
Would it be a violation to play back a record like a CD and have a digital buffer? That would be pretty silly.