Blatantly copying somebody's magic trick from which they make a living from and then literally packaging and selling it as your own is downright dirty.
I love Penn and Teller but I was pretty bummed to read this story, it's so anti-competitive, and Penn's comments smacked of elitism, especially about how "elegant" the "real" way Teller did the trick was.
I think the issue here is that he's taking the performance whole-sale rather than coming up with a similar illusion. Teller offered to buy him out, which I think is a combination of class on his part and recognition of the nature of tricks in professional magic.
It'll be interesting to see what happens.