A better way to put my argument is: could an average mom build Linux on specialized hardware in space? If the answer is "yes", then you may have a point.
I don't think the answer is yes.
Just because you can read it, doesn't mean you can or will be able to actually fix it; not because of technicality, but because of personal knowledge.
In this case, they are both black boxes.
I once spent three days trying to figure out an issue, stepping line by line through hadoop (after figuring out the issue was in hadoop and not my own code). Yay, I proved the issue was actually in Java itself. Guess what happened next? We avoided the bug. Why?
- We couldn't update Java.
- We couldn't change hadoop because we were using a packaged solution. So, we just filed a bug with them.
Had the source not been available, we would have just skipped all of that, and it would have been our vendor's problem 3 days earlier.
This happens less nowadays, because stuff like Android and ChromeOS, so why pay Microsoft when free beer OSes exist.