Re: Quick to fix in Open Source, but it leaves questions.
"It was made by many, and repeated over and over."
Proof?
" where's the proof? The link you post is just a sample of a single application"
A single application that leaves 7600 national-security-grade very large plants wide open to pretty much any script-kiddy with no particular skill. Trawl tech news and you'll find plenty such examples, including powerplant control software and the like. Looks pretty serious to me.
"And yet, to patch some code, you need someone really skilled and with a deep knowledge of the application domain"
True
" - plus a whole build and test system s- sometimes you can afford both, sometimes you can't, thereby there's very little difference if the code is available or not, you're in the hands of the code/application supplier anyway."
Also true.
But in one case you get something that you -or someone of your choosing, or anyone- can check. In the other case you get something that you can't check, that you KNOW may have not been checked by anyone (because who has spare money for extensive checks when they know that you already paid and no-one can point the finger at you, ever, anyway?).
Sorry but put in the light of pure profit logic, your post suggests that closed-source software is necessarily bad. Now my guts tell me that it's not what you mean. Peraps the problem is that you posted this on your spare time, that would explain why your argumentation is blatantly full of holes. You should hire someone to make the argument for you. I'm pretty sure it would be better (can't be worse anyway).
Oh, just so that y'all know: most open source developpers are not unpaid enthusiasts: they are skilled developpers who are paid for their work and don't fear putting their own name behind their work. The same ain't true for closed-source software.