Nah they use “an open standard” being just markdown files or something, but the apps are still proprietary as far as I’m aware
I really hate how I sometimes, though rarely, see Obsidian talked about as if it were open source just because it uses an open standard
Like Photoshop isn’t open source because it can use PNG kinda thing
“I fear not the man who can make one thing in 10,000 languages, but I fear the man who can make 10,000 things in one language.” - Bruce Lee