[jaguar]

No they fucking didn't.
Firstly, layout code is copyright. Copy it, you're breaking the law and liable to be sued for damages. Secondly design is copyright, copy a book cover or an illustration and see how far you get with that one in court. Thirdly, interface elements can be covered by copyright and patent law, take a look at Adobe vs Macromedia. Last of all, Apple and Microsoft reached a settlement.

Sure, you can take ideas and re-impliment them if they are not covered by patents and considering the complexity of some interfaces today you better use proper clean-room techniques all the way but you cannot legally directly copy things. The web isn't what it used to be, hundreds or thousands of man-hours go into projects like Google Maps, just because you can see some of the code doesn't mean you're allowed to copy it.