Re: Daniel Belin is right
"Stole" is a bit strong! They could certainly be accused of stealing popular credit for inventing it, but I'm pretty sure they had an open 'go ahead and use these ideas' from Xerox. That was sort of the point of Xerox inviting them (among others) over for a look-see in the first place.
As to them trying to sue anyone for 'copying' the GUI concept from them, yes they very much deserved to be thoroughly trounced on that one, though!