While I do agree that it’s the user’s mistake for not noticing the fine print on the download page, this probably should be made a bit more obvious upon launching the software for the first time, or when logging in to activate the demo.
This is especially relevant when compared to other types of software that 3D artists are most commonly adjusted to using, such as *****, which do include the ability to open projects that were created in trials, demos, and student versions (as someone mentioned earlier).
It’s currently very easy to make that mistake, and results in disgruntled customers after they’ve just invested money in your product. Probably not a good look when you’re wanting positive word-of-mouth…
On the subject of the restriction itself, this “is” the sort of product that takes a lot of work hours to assess whether it’s going to be worth using for a specific project, since it can take a very long time to align images and then reconstruct for a usable model. Adding control points is half of what results in a good outcome, and that is also quite a lengthy process. While I understand where the developer is coming from in terms of “doing all the hard work in the demo and then using a paid license for export”, perhaps it’s a bit unreasonable to rob the user of a couple of day’s worth of work/testing, when the minimum spend for your software is 3 months worth either way?
Personally, I’d be more than happy to leave the software running for the automated processes again upon upgrading to a paid license, but the manual labor involved with assigning control points is time I just wouldn’t be able to get back. A better option might be a 14 day trial (without export functionality) which includes the ability to import the trial project into the paid version of the software, maybe with a requirement for re-processing the model before export.
I don’t really think either either party is at fault or being unreasonable in this discussion, but I hope this is some user input that you can use for future licensing decisions. Cheers.