Microsoft did what Samsung did not and that is why Apple is suing Samsung.
Today during the Samsung Apple trial it was revealed that Apple has licensed its design patents for the iPad and iPhone to Microsoft. Apple offered Samsung a patent licensing offer back in 2010 that the Korean company did not take.
The Apple license for Microsoft has a clause that they are not allowed to make clones. That is why Microsoft's Windows 8 touch interface looks so different compared to the iOS UI.
It is not known what Microsoft pays Apple for the design patent licenses.