Lots of apps have open-source clients (for trust/auditability) but backends that are closed/locked somehow, e.g., Logseq.
There are a bunch of small problems people encounter here and there, which usually will never be solved by the company. Giving the community a route to improve their tool, would be good.
I think we will soon see the ability to write plugins that can even run server-side of SaaS solutions.
I don't particularly like client-side paid features, but:
- The client is fully FOSS, you can just patch the license check out. In fact, there are some forks on GitHub that do just that and provide binaries, and the authors don't seem to care, they even acknowledged them on Twitter (https://x.com/b3logos/status/1928366043094724937).
- There are plugins to sync without a paid plan
This works out quite well for them: if you choose a fork or a sync plugin, you don't get the same support that paying users do, so many users still end up buying a license. But you don't need to, which makes the whole thing not user-hostile.
I have bought a one-time license myself, and I'm very happy that I'm supporting the development of a FOSS project.