I wanted to wipe my PowerBook clean, so today I bought a Leopard disc (because I couldn't find my installation disc). It worked, but I was wondering if my friend could use the Leopard disc. Is it a one-time use sort of thing?
Well, I think it is, as you say, a "one-time-use thing". I believe when you buy mac software, it comes with a code that you use to register your product. So yes, as far as I know, it is only one use. Otherwise, Apple could lose profit!
Like Noels said, for one machine/owner. You can install as many times you want on that machine, but you can not legally install on another machine as long as it's installed on the original machine.
Also you can not let anyone outside your house use your Leopard DVD either. That is also against Apples EULA.
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