Digital Research, Inc. is a hallowed name in the industry. The company was founded by Dr. Gary Kildall to sell and further develop his CP/M operating system. In the first half of the '80s, DRI developed an implementation of the ISO standard Graphical Kernel System, a low-level system for 2D vector graphics, called Graphics System Extension. GSX eventually formed the basis for GEM.
GEM, or Graphical Environment Manager, was to serve as DRI's graphical user interface on top of CP/M and later DR-DOS and other versions of DOS. GEM's star shone particularly bright as the user interface for the Atari ST, a computer that competed with the Amiga, the original Macintosh, and earlier versions of Windows.
Apple wasn't happy with having to deal with competition, so the company started to sue everyone it thought it could get away with. We all know the lawsuit against Microsoft over Windows 2.0, which Apple eventually lost because Microsoft had actually licensed much of the GUI technology from Apple - Cupertino claimed this only covered Windows 1.0, but the courts disagreed. Ten elements were not covered by Microsoft's license, but the courts ruled that these were not worthy of protection.
Interestingly enough, Apple didn't just sue Microsoft over look and feel - two other companies were sued as well: Hewlett-Packard and Digital Research. The suit against HP was about NewWave, an object-oriented desktop system that ran on top of Windows. This lawsuit was part of Apple vs. Microsoft, and Apple lost it as well. The lawsuit against DRI, however, never fully materialised, because DRI wasn't looking for a prolonged legal battle, and as such, decided to make several alterations to GEM/1.
This resulted in GEM/2. The trash icon was altered, the desktop was replaced by two permanently open, fixed file manager windows, scrollbar blobs were made narrower, and animations were removed from the system. The goal was to please Apple into not suing the heck out of DRI, and this strategy eventually succeeded. A few small cosmetic changes, and GEM continued to exist in several forms for years and years to come.
The cool thing is that GEM had several advantages over the Macintosh, and two of those are pretty damn huge: GEM supported colour interfaces, and, more importantly, it could multitask. In other words, it had two high-profile features the Macintosh didn't offer, much like Windows 2.0 and NewWave.
However, that's not the common thread between Apple's lawsuits against Microsoft, HP, and DRI. You may wonder why Apple never sued Commodore for the Amiga, which also sported a graphical user interface containing several of the elements Apple claimed ownership over. It's actually quite simple: unlike AmigaOS and its Workbench, Windows, NewWave, and GEM all ran on DOS... And more importantly, on IBM-compatible PCs. Considering IBM was Apple's biggest competitor, the company was adamant in ensuring the graphical user interface did not find its way to IBM-compatible machines.
That's why the argument about copying/stealing/whatever is laughed away by those of us with an understanding of history. Apple sued Microsoft, DRI, and HP not because they felt wronged, but because they were afraid of the competition that would result from these companies bringing credible user interfaces to IBM-compatible hardware. Since the Amiga was a separate and unique hardware platform, Apple knew Commodore would not be able to compete in the long term, so it didn't bother to sue Commodore. Apple's fears became reality - the Amiga withered away into irrelevance and the IBM PC took over the industry - and it nearly killed Apple.
You can easily draw a parallel to today. Apple didn't sue over WebOS or Bada (which looks virtually identical to TouchWiz, I might add); they sued Android, because it's basically today's IBM-compatible platform. You'll also note that the focus of Apple's legal actions used to be HTC, but when Samsung rose to prominence in the Android space, the South-Korean company became the focus instead. Anyone even only slightly versed in pattern recognition can see the obvious.
You know what the irony is of all this? One of the main developers behind GEM was Lee Jay Lorenzen, and get this: before joining DRI, he worked at Xerox PARC on the very same user interfaces upon which the Macintosh was built. In other words, Apple took what was partially his work, implemented it for the Macintosh, and then sued over Lorenzen's own post-Xerox interface!
The irony is so thick here you could cut it with a knife.