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.