I haven't been able to find this via Google. In particular, I am interested in reading about whether or not a Snow Leopard license is a prerequisite for installing Lion, and the new virtualisation rules.
Does anyone have a link to this?
All Apple's hardware & software product agreements can be found at: http://www.apple.com/legal/sla/
Here's straight link to Lion's agreement.
Answers to your particular interests can both be found under § 2. B:
[…] you are granted a limited, non-transferable, non-exclusive license:
(i) to download, install, use and run for personal, non-commercial use, one (1) copy of the Apple Software directly on each Apple-branded computer running Mac OS X Snow Leopard or Mac OS X Snow Leopard Server (“Mac Computer”) that you own or control;
(iii) to install, use and run up to two (2) additional copies or instances of the Apple Software within virtual operating system environments on each Mac Computer you own or control that is already running the Apple Software.