Is anyone REALLY surprised?
I'll bet they do whatever it is they have done to Final Cut Pro. As of FCP 3.0, CD-R copies and disk images of the original CD's do not work. I'll bet they implement the same thing on 10.2 and beyond. Also, a "key" that you have to type in is not, nessesarily a bad thing, but I hope they don't move to the "you have to register with us" horror that Win XP was supposed to have (or does have).
As an answer to the above question - Yes, you are supposed to buy a copy of OS X for each Mac you run it on, don't you? This is true for most (if not all) commercial software. (Gotta read those EULA's) And it makes total sense too, using the logic that one copy can go on multiple machines, why would a company or school buy licenses for 100 Mac's when they could just install the same one over and over. Installing a single lincense of OS X on more than one machine is no better than burning a copy at your friend's house or pulling it off HL or the like. If only one machine is every booted up, then you have an arguement for it to be okay, but not if you're running it concurently on your PowerMac and on your Powerbook and on the downstairs iMac and on the... well, you get the idea.
BTW, At the FCP 3 roadshow, when this came up, a bunch of people said they thought it was akay to install one copy on multiple machines, as long as they were only using it on one machine at a time. (ie. A PowerBook & a PowerMac) The presenter had to say that Apple's stand on it was for one copy per install. (Although he sounded like a recording when he said it and I'd bet he'd agree with anyone who used it as such.)