While the underlying idea that selling services on open source products is not sustainable from a purely business perspective may be true, the linked article is not particularly convincing to me, it doesn't provide strong evidences and it's based on an embarrassingly small sample size. Besides, maybe we should start to consider also other metrics when we evaluate a Business success, not only the mere economic profit: there are externalized societal benefits (and damages) that are very important and nonetheless poorly accounted for.
It only looks at one open source company, that could not have closed source its product (because it was not the original developer) so it could only exist at all as an (at least mostly) open source business and compares it to companies in entirely different lines of business.
It was also badly outdated a few years after the article was written when the said business was acquired for several times the market cap at the time the article was written.
If you want to compare it to businesses offering a similar product into a similar market you should compare it to other OS vendors founded in the 90s targetting desktops and servers. Any more successful proprietary examples around?
Most of all the article only looks at one, open source business. Not exactly a meaningful sample.
It is probably very difficult to rely on that model if a single company is the original developer and the main developer - so you have all the costs but share the benefits. It is not true if you fork code that already exists, or if you have a bazaar development mode.
