>An open-source software on the other hand might not be maintained in 10 years from now, but people (like a government agency) can always fund further development, if they really, really need it alive. Open source never dies.
At the government department or big organization level, they can fund or perform any proprietary development they need themselves as well. FOSS just isn't necessary at that level of resources. For ordinary users FOSS provides essentially zero comparative benefits over proprietary. If code doesn't have the features they need, goes unsupported or has bugs, they're in the same boat regardless. People choose to pay for software for valid reasons.
"they can fund or perform any proprietary development they need themselves as well"
Try phoning up Microsoft and asking them how much it would cost to add a feature for an old piece of DOS software that they haven't touched in the last 20 years. I suspect the answer would be at least 8 figures, if not 9.
The point is, an organization at that scale can solve problems at that level because they have the resources to fund development of an alternative that e.g. doesn't rely on DOS. Individual users don't have the funds to do that, or the skills to develop new features themselves, so once it's no longer supported they're equally screwed whether the software they rely on is FOSS or proprietary.
If the software is open source, you can relatively easily find somebody to do it for you for $100/hour or so. That's within the scope of many individuals.
$100 000 000 is outside of the scope of pretty much everybody.
Relatively easily. Really. Your solution is for ordinary non technical people to become development managers and hire someone they don't know to do something they don't understand at their own financial risk.
How can they not understand it? If the consultant does his job, the software will work. Any idiot user can tell if the software actually runs or not.
People hire mechanics to fix stuff all the time, even though they don't really understand how their cars work. They do know when their cars aren't working though.
You're trying to convince me that ordinary people are utterly incapable of hiring experts to perform services for them?
How do they know how much work the change will take? How will they know what a reasonable fee is for completing it? How can they verify the solution's quality beyond a limited demo in controlled circumstances? Even if the payment was kept in escrow by a third party, how can they be sure they draft the requirements for payment in such a way that they can avoid a technically valid but practically useless end product? They would be completely at the mercy of an unscrupulous developer.
At the government department or big organization level, they can fund or perform any proprietary development they need themselves as well. FOSS just isn't necessary at that level of resources. For ordinary users FOSS provides essentially zero comparative benefits over proprietary. If code doesn't have the features they need, goes unsupported or has bugs, they're in the same boat regardless. People choose to pay for software for valid reasons.