Is it? I boot my Mac into Windows fairly often. And that's irrelevant anyway, because HP is not selling an OS, they are selling hardware that happens to look extremely similar to an iMac.

In fact, on that first photo on the linked article I genuinely thought they had placed an Apple wireless keyboard and magic trackpad in front of the HP computer. And the only reason I knew that wasn't an iMac was because of the lack of the apple-logo-on-aluminum bar at the bottom, which was simply replaced by an HP logo in the exact same spot.