Actually, Mac OS X charges for each upgrade-about a hundred bucks every year and a half or so. Yes, you get a copy with a new Mac or recent used one, but it's off to Craigslist for those of us with older Macs. 10.4 is kinda the place to stop with a G4 anyway-10.5 is pretty hardware intensive and 10.6 doesn't support PPC at all. I've got real Apple factory DVDs of every Mac OS from 10.0 to 10.4 but until I do a hackintosh, I'm not going any farther.

FWIW, I can pick up G4 towers here for less than a hundred bucks all day long, Quicksilvers are cheap and plentiful.

To use my example again, four hundred US dollars for two OS copies on two boxes is painful. Five hundred bucks for five of them is much more doable, at that point I could give boxes to my friends to propagate. Keys already paid for, problem solved, savvy?