Hi, I love Obsidian. It's part of my daily routine since a year or so, and I use it to store all my work and personal notes for the future. The main reason I use it is because of its note storage method. Instead of relying on a database, it utilizes plain text files written in Markdown, as most of you already know.
However, I have a strange feeling about it not being open source. The recent events with Reddit have only increased this discomfort. My notes are in plain Markdown, so I have the assurance that no one can forbid me from accessing them. I also take precautions by creating multiple backups, which provides additional security against virtual loss if I handle things correctly (which I do).
That being said, I would love to have alternatives like Joplin or LogSeq that adhere to the same philosophy of work as Obsidian.
Joplin is not suitable for me due to its reliance on database storage. I prefer to have total control over my notes.
On the other hand, LogSeq is more focused on serving as a diary rather than a personal knowledge manager, and it does not use pure markdown, wich will be a problem in the future when (not if) I'll need to migrate out of LogSeq.
I am pretty sure that not being open source is not a problem. Again, many people said here, Markdown is pretty much future-proof and mostly independent of any app that you use. The only problems you might encounter are some formatting issues (like Wikilinks, which are not default in Markdown standart) and, if you rely heavily on plugins, JavaScript and TypeScript development, in my opinion, can be a bigger problem, because, you know, these things belong to Oracle