To be fair, when someone comes up with excuses for not making something open source, it comes off as dishonest. Be honest. Say that you want to keep it closed to keep control and make money. There's no need to say otherwise. I do the same. I keep code private to make money. I don't say more than that.
You'll see a plethora of such apps made with LLMs. People will write something custom to meet their own needs and to have the features they need.
If you look at my GitHub profile[1] you'll see that the majority of my time is spent on open source. But my priority is open sourcing the tools and libraries I would want if I were building an alternative to Obsidian (Defuddle, JSON Canvas, Web Clipper, Importer, Flexoki, etc) because I believe all software is ephemeral and that files matter more than apps[2].
Obsidian is a free app made by seven people. If we were purely financially-motivated there are many levers we could have pulled, e.g. adding feature gates, not allowing alternatives to our paid services into the official directory, etc. But as I wrote in the tweet linked above, I have spent decades making open source projects and those have never paid the bills. So yes, there is some financial motivation behind that decision.
This is a wild take even coming from HN. Nobody needs an excuse to not make something open source.
This sort of entitlement does, and has done, far more damage to the OSS movement than anyone's "excuses" for not open sourcing their code. Full stop.
You can absolutely prefer open source software and choose not to trust closed-source apps. That’s all fair. But treating closed source itself as evidence of deception or impending betrayal is exactly the kind of ideological purity test that makes these conversations exhausting.