All right, that’s an argument. Also, having fun from coding is also a valid argument. Though, from my experience, it is easier to start learning programming from some simple, isolated cases, as in thextbooks, than from real life programs, which can be very nasty and domain-dependent.
Forgive me if I trivialize, but we should not mourn too much: the obvious solution is to pirate it all. Do not waste time and energy for reinventing the wheel in the form of writing open source software. These resources can be used better for Revolution. Instead of diving into exhausting dispute and overintellectual arguments of Stallman, just do what said Marx: seize the means of production. That is, fucking pirate it. It is simple as that.
One time, I spent whole day arguing with some anarchkiddies about that, and no one gave me a short, convincing argument like that. Their posts were emotional rather than seeking for truth. That’s the difference between debate and dialectics.