First, from the article:
The full court documents go into some details about the reasons for the decision. It explains that "the requirement that the unregistered trade dress 'serves no purpose other than identification' cannot be reasonably inferred from the evidence" (trade dress patents cover design elements that are functional as well as aesthetic) so a recalculation is in order.
The article is confusing two things here... First is trade dress, which is part of trademark law and covers the look and feel of something. It's under the commerce clause of the Constitution, and is codified in the Lanham Act at 17 USC 1051-1127. Trade dress is also a common law doctrine (and some states, particularly the original colonies, have their own state trademark law), and accordingly, there is such a thing as unregistered trade dress rights (there are also registered trade dress rights).
Second is design patents, which are part of patent law and also cover the look and feel of something. It's under the patent clause of the Constitution, and is codified in the patent act (35 USC 100 onwards). There is no such thing as an unregistered design patent or a "trade dress patent".
Finally, neither trade dress nor design patents can cover functionality. They only apply to aesthetic features or "surface ornamentation".
"But wait, Theaetetus," some Slashdotters protest. "Rounded corners are always functional, because otherwise, you'd cut your fingers off on the sharp edge!"
That's true, and neither the trade dress nor the design patents cover the concept of rounding a corner... Instead, they cover this specific radius of curvature. Specifically, why would you choose rounding the corner? To avoid sharp edges. Why did you choose a 1/8" radius instead of a 1/6"? An arbitrary aesthetic design choice.
Moving on to the real point here...
The jury found that Samsung infringed the (i) unregistered trade dress, (ii) registered trade dress, and (iii) design patents. With regard to the first one, the unregistered trade dress, Apple has the burden of proving that it's nonfunctional. They failed to do that, because the design as a whole offered some utilitarian advantages. So the damages placed by the jury because of (i) should be struck.
Turning to (ii) the registered trade dress, this had nothing to do with rounded corners. The registered trade dress covered the 16 icons on the iPhone's home screen. The Court held that those icons have functional features, since they tell people whether they're clicking on email or a browser. So, since they're functional, the damages placed by the jury because of (ii) should also be struck.
That leaves us with (iii), the design patents. Here, however, the jury was instructed to disregard any functional elements and focus just on the aesthetics. And here, Samsung loses, because they can't show any error in that.
So, the jury award is reduced to just what is applicable to the patents, not the trade dress.
As an aside, the court also upheld the validity of Apple's utility patents over Samsung's objections. So this is a net loss for Samsung.