All software should be free-as-in-freedom, but not nescessarily free-as-in-£; though I acknowledge that the former without the latter is often problematic. Plus, even beyond the "moral should", practically speaking, going non-FOSS this means it gets excluded from GNU/Linux distro packages, which IMO would be a fatal hit for something like this.
But honestly, I'm fine with this move. It's still FOSS for FOSS-systems, while support for non-FOSS systems is non-FOSS. The folks who care about free-as-in-freedom won't be affected by this. And even then, the non-FOSS `sold` is source-available, which covers 3 of the 4 freedoms; and IMO that missing freedom is the least important.
> I still suspect they won't succeed. How many businesses are so constrained by link times on Mac that they're willing to pay to reduce them? (And go through the admin effort of paying for something.)
A reasonable amount of software is "free-as-in-£ for personal use, paid for professional use." Lots of orgs are willing to ask individual devs "are there any dev tools you use that we should be paying for" and are willing to pay the $50/mo for IntelliJ, so $10/mo for `sold` seems to me like it stands a chance? Note that `sold` is still free-as-in-£ for use in CI/CD, and is only paid for individual-developer use.