[aeturnum]

The developer time it takes to do bug fixes and minor features is not free, so it seems appropriate to charge a fee for it.

I know that it's very common for subscription models to coincide with forced upgrades (as this one does), but that seems like a choice on the part of the company as opposed to something inherent to the revenue model. I'd be quite happy to pay a developer to continue to maintain an older version of their software.

Like you pointed out, I think a fee structure where you pay for major updates and otherwise pay a maintenance / hosting subscription fee makes the most sense.

I think that you see open source projects that struggle along all of the time because their developers cannot afford to work on them enough. Not every project, but enough of them. I try to support projects like that too.