Of course, ALL booksellers use DRM. This is all a nice way of sidestepping the fact that those booksellers all prevent Apple (or indeed books from other booksellers) being sold (or often even) read on their devices. The "open Amazon"

has its own DRM, own format AND own closed device.
Apple allows books from ALL those sellers on its devices. They all want to play on Apple's lawn. Apparently they don't want Apple on THEIR lawns.
I'm beginning to think that you guys are in AMAZON'S pay. Two can play in that silly game, after all.