I’m not familiar with it, but it looks like it’s a Proprietary and Freemium product.

If you want a similar product that’s open source and privacy focused, check out memoria. There is a one time payment though.

And there are other open source ones like StoryPad (free, ad-free, privacy focused), Diary Vault (free and ad-free), and Pile (freemium).

I’m not saying this with any snark or sarcasm - But if you really want a journaling / diary experience that has 0% risk of a company mishandling your private data, pick up a pen and paper. Remember to always ask if you really need a digital tool to accomplish your goal, or if an analog version of something with suffice.