Yes, and often when the OS has had a major revision a new version comes out as a paid upgrade (or more often lately, a purchase includes upgrades and maintenanc

Yes, and often when the OS has had a major revision a new version comes out as a paid upgrade (or more often lately, a purchase includes upgrades and maintenance for a certain time). Though it is work the developer has to do regardless, if they want any new sales. And maintaining the software is orders of magnitudes cheaper than develop it from scratch so it is kind of weird to latch on to the maintenance aspect. If your sales paid for all the initial development then it will pay for maintenance. A bigger worry than the maintenance aspect is, will I recoup my initial investment? The cost will always be arbitrary, software costs nothing to "manufacture" so any one-off payments or subscriptions will only match the costs associated costs for a certain scale. I agree with what you say, sustainability is crucial. Doesn't follow that subscriptions are the only solution. Subscriptions-is-the-only-sustainable-model is the narrow-minded view I mostly see on HN. Undoubtedly because the audience are developers.