[slick70+]

Can someone tell me whether I'm allowed to install my copy of Tiger on an external hdd & boot from that? I mean, is it legal? Do I have to uninstall the original?

What happens when I buy Leopard. Do I need a separate copy for my mini and my ibook or can I use it for both?

Sorry, I have no idea how Apple's licensing works....

[peeb]

You can boot from an external HD, but it is one copy = one machine, unless you have a household license.

[Dork.]

Apple doesn't do any dippy Product Activation, at least not yet. But one retail copy should be running on only one computer at a time. If you violate this, Steve Jobs will wag his finger at you through the Internet!

Apple's "Family Pack" is a very good deal, and I've bought it ever since our household gained multiple Macs. Single retail copies of Apple OS's tend to go for $129, while the Family 5-pack (meant for only computers in the same household) is $199. It's like getting the second license for half price, and the rest (up to five) free...

You get the pleasure of knowing your software is legal, and Apple makes an extra $70 by simply putting a license addendum sheet in the box (Seriously, that and the sticker on the box is the only difference between the single retail copy and the Family Pack!)

[peeb]

Yes, Apple is very reasonable about trusting users not to abuse this, and, in my experience, users don't abuse it a whole lot, not wanting to end up in the Windows situation where it's a major PITA to activate etc, and you are treated as a criminal each time you boot.
Do the right thing, it's better in the long run!