@Mike
>If Apple spend time and money developing an operating system why
>*shouldn't* they be able to dictate the conditions on how it's used?
They probably could, (to a point,) with an explicit license agreement between them and each customer.
However, with EULAs in general it is my understanding that the provider of the software takes the stand that since they hold the copyright, anyone making copies must have a license from them to make copies of the software and this license is granted only when the terms of the EULA are met; since using a piece of PC software requires making copies of the same on the mass storage medium (installing) and RAM(/swap) (running), an EULA effectively applies to its use as well.
To make an EULA work the provider of the software is relying on the protection of the copyright laws. This is where it gets interesting, however: for example here (*) the law explicitly allows for making the copies of a computer program that are necessary for running the same, which would seem to thoroughly wreck the legal foundation of an EULA as presented above.
(*) Finland, the rest of EU is likely to be similar (?)