Sam:
I respecfully disagree. I am a computer science major, not an artist, and even though I can put skins together sometimes I look at other skins to see how they have accomplished a certain visual effect. It is not my policy to borrow, steal, use without authorization, the skins others have developed by the way.
I think that the article in question is a great teaching tool. Maybe the DNN Corp. should talk to them to borrow it, with permission, and make it available on the DNN site. Or maybe, they should have used one of the skins that come with DNN as an example. Anyway, it is not the first time that someone has "reversed engineered" the DotNetNuke.com site's skin, if you look in the forums there are several instances of people asking how some of the visual elements have been accomplished. Plus, you have to give them credit for clearly explaining the possible copyright issues and prominently displaying the DNN site's URL all over the article.
Also, because all elements of any given skin are easily retrievable from any DNN site, I think that this kind of "reverse engineering" is done a lot, maybe this is the dark little secret of skins designers. 
Carlos