A retail copy of OS X will work on any number of machines of any type.
A bundled (with a Mac) copy of OS X will work any number of times but only on that type of original Mac (Macbook, iMac, Mac Pro, etc).
The licensing is not enforced, but they have a very low pirate rate due to the user base being 80% + on the latest version and the bundled OS with a new Mac.
A retail copy of OS X will work on any number of machines of any type.
A bundled (with a Mac) copy of OS X will work any number of times but only on that type of original Mac (Macbook, iMac, Mac Pro, etc).
The licensing is not enforced, but they have a very low pirate rate due to the user base being 80% + on the latest version and the bundled OS with a new Mac.