Yes, it's absolutely mathematically correct, while being entirely uninteresting when taken in its strict mathematical meaning.
When a motivational speaker says something like "Billionaire X proves that it's possible to be a billionaire" that's mathematically correct, yet totally uninteresting. What people go there to hear about is methods for reproducibly becoming a billionaire or even just slightly increasing your odds of becoming a billionaire, and this article is just as lacking in that department as most motivational speeches.
Don't get me wrong. I think open source is a good thing. It seems like the author is working hard, doing good work, sharing it, and making a solid livelihood may be well-deserved for him. There's just nothing here that suggests a reproducible method.
Prove is the technically correct word here, in the sense of mathematical proofs: the existence of an example proves that it's not impossible.