I’ve downloaded and installed Mountain Lion (10.8) on several machines now, but I never paid for it. No, I didn’t pirate it, I got it from the App store, but it never gave me a chance to pay. Looking up the transaction in the App store via iTunes, I see this:
In other words, I did “buy” it, but got it for nothing. Officially. What I don’t get is why. I’m just guessing here, but since I’m a registered developer on the same account, and I’ve run the developer previews, that earns me a free release version as well. (Note that the 10.8 above is not a developer preview, but the released public version.)
Nice gesture, Apple. Unless it’s an error. If so, I really don’t mind paying for it; it’s not exactly expensive.