The confusion – that Open Source is based on altruism – is a dreadful mistake. Speakers who argue that it happens due to the unselfish concern of developers for others, are simply unable to understand what is happening.
Those who say Open Source is altruism think of knowledge as a scarce resource, that only altruistic persons would share. The opposite is true: knowledge is an abundant good. For “trading” it, you get attention, trust, authority, etc. – all the things that help you to further develop your expertise and be successful.
As long as you don’t understand that point, you won’t understand the knowledge economy of Open Source. To extend Wheeler’s statement: Open Source is commercial when it comes to making money as well as “buying” knowledge with knowledge. This has nothing to do with altruism.