I had a question about the legality of duplicating the design of a commercial OS to an Open Source desktop. Let me just cut to the chase.
Is it illegal to create a Desktop Window manager that behaves like, and looks like the Macintosh GUI?
As far as I know, patents in Desktops are applied usuaislly to the interactivity concepts. The color pallete, font size, menu items, i.e., the style are not patentable. What can be patented are the concepts of a desktop - such as: a dock and finder (their interactivity and possible algorithm).
Since the style is not patented, many FOSS substitute applications clone or inspire the GUI style of their proprietary versions (examples as: Cheese and Photobooth, Pidgin and MSN).
Now, shipping the desktop GUI with a patented concept such as a dock can infringe patents. So, in the end the company needs to be careful to use abstract interactive desktop concepts on their GUI.
Side note: The problem with patents is that usually they are very very broad. For example, in the dock component patent we can definitely fit the Ubuntu Unity and Windows 7 Menu.