Each version of the SLA is for that particular version of OS X indeed. In the SLA it discusses what you may and/or may not do with that particular piece of software. However, it does not mention anything about previous versions of OS X nor anything about future versions anything other than updates and upgrades.
Apple is not above the law nor are they the law. Apple can want it a certain way but ultimately it is law that will decide. There are certain countries where you have to be very specific with certain aspects of a license agreement and where judges will have a different interpretation of the license agreement than Apple and/or the user. We've seen this with the license agreements with iTunes and the various other stores Apple has, as well as the warranty thing. In many other countries Apple had to change the license agreement. If you take a proper look at the license agreement for say, OS X Mountain Lion and thus read beyond the first few pages in English you get a completely different view of the license. In German it says the following:
(iii) Zum Installieren, Nutzen und Ausführen von bis zu zwei (2) zusätzlichen Kopien oder Exemplaren der Apple Software innerhalb virtueller Betriebssystemumgebungen auf jedem Mac Computer, dessen Eigentümer Sie sind oder der Ihrer Kontrolle unterliegt, zum Zwecke der: (a) Softwareentwicklung; (b) Durchführung von Tests während der Softwareentwicklung; (c) Nutzung von OS X Server; oder (d) der persönlichen, nicht kommerziellen Nutzung.
The entire part of needing to have the Apple Software running on the machine is left out. That might have some consequences in other countries that do have the requirement for Mountain Lion as a host OS, especially in the EU (there are already lots of legal issues with the App Stores: not having an App Store for each country but 1 App Store for the entire EU).
Btw, how this SLA is presented also opposes problems. There are countries where this SLA has to be told or otherwise handed over to the customer before opening or using the product. If they don't then the license is unlawful and thus anything that is in the license does not apply. In the Netherlands there are some issues with this. It is unknown if Apple's SLA is lawful due to the way they are letting buyers known about it (they have to be told upfront, not when they are running the installer, it has to be put outside the box but the question remains if putting a hyperlink that is only English is enough).
Like I said: it is not as simple as you are depicting it. The best option is to ask a lawyer since that person knows the law of your country best (it actually is what Apple is recommending you to do in the beginning of the SLA). Ultimately it is indeed up to the user what to do. Let's not forget that there are many nationalities visiting this forum thus there will be differences when it comes to law, licenses, etc.
Message was edited by: nb Text layout was b0rked