I don't think the article rigorously defends its position. Just because a company innovates after being copied does not mean it is innovating because it was copied. The article doesn't give one example of a situation where a company was motivated by being copied (or even a solid reason why they would be motivated by that).
I'll explain the correlation I see: products that are bound to be very profitable are bound to be copied, so of course a company like Apple will develop something like the iphone despite potential copycats.
Sorry, I don't see the article saying that a company innovates because it was copied. What it says is that being copied doesn't stop innovation — which is the whole premise of the IP system (if I can't recoup my R&D costs, then I can't afford to innovate).
You're right, the article argues that copying doesn't stifle innovation, but it goes beyond this and argues companies innovate because they are being copied. For example, this quote argues a correlation between copying and innovation, and hints at a causation:
>Being copied didn't stop or slow their ability to innovate at all. If anything, it only seemed to accelerate it. Apple wasn't able to rest on its laurels; to return to profitability, and to take the mantle they hold today of one of the technology industry's largest companies, they had to innovate as fast as they could.
I'd be the first to agree that an open, competitive market is a good thing. But the author is explicitly discussing "copying", which usually involves an infringement of IP a company considers novel and important to their competitive advantage. I wouldn't say the author's point is completely without merit, there's a balance at play. If the balance goes too anti-patent, companies would be better off investing very little in innovation and a lot in copy-cat products that can undercut true innovators. If Apple never existed, Samsung may today be selling 2008-era phones for 500 dollars. That's the risk.
If that's true, given that Apple felt it was being copied by Microsoft in the mid-1990s, took them to court, and lost — I'm not sure how much more "anti-patent" you can get for Apple than losing a case on its core product — then why did they bother to invest in creating all that stuff that's got them to where they did?
And, if an "anti-patent" causes companies not to invest, then how come, five years after the release of the iPhone, with it still not clear whether patents are being upheld or not (but not looking good in Apple's favor: http://www.bloomberg.com/news/2012-07-09/samsung-wins-u-k-ap... ) then Apple continues to invest in the iPhone?
I'll explain the correlation I see: products that are bound to be very profitable are bound to be copied, so of course a company like Apple will develop something like the iphone despite potential copycats.