Yeah the parallel to open-source software is quite interesting. Notably that the license doesn't prohibit resale. Ultimately though, they both face the same challenges: time. The only reason the guy was able to do this was because his parents sponsored his flights and he had the free time. FOSS developers are only able to work on their projects when they have the time or sponsorship. In both cases the usually argument against them is that they are "amateur", but like we can see, amateur is usually good enough for most people as opposed to paying. Like you said, those who need custom work will be willing to pay and the software industry is doing just fine. In fact, one could argue that FOSS actually enables businesses by reducing startup costs—even big companies are known to use certain libraries.