I don't see the difference. Google pays smart people to write proprietary software that they sell users access to. Amazon pays smart people to write proprietary software that they sell users access to.
The difference is that the author read a Google recruiting ad and is comparing it to Amazon's publicly-available products. Yeah, they're different. Users don't care about petasort. Recently-graduated PhDs looking for work do. And that's who that copy is targeting.
No, you're missing the point. Google pays smart people to write proprietary software that they don't sell users access to. Are you confusing the sale of ads with the sale of the software that allows the ads to be effective? Google's sale of their products would be analogous to Amazon allowing sellers other than Amazon.com to sell stuff through their web store. And they do!
The point of the article is that Amazon also sells the web store itself. Google has interesting, proprietary software, but they don't sell search engines, sorting tools, or scalable web hosting.
Okay, so they don't sell sorting tools. But to be fair, they've published a number of papers on different technologies which have furthered the creation of a number of tools, including sorting tools.
The difference is that the author read a Google recruiting ad and is comparing it to Amazon's publicly-available products. Yeah, they're different. Users don't care about petasort. Recently-graduated PhDs looking for work do. And that's who that copy is targeting.
"Nothing to see here: move along."