If you prefer to, you can simply clone the repository and set it up yourself on any hosting provider, for free. I'm just asking that you don't try to make money out of it yourself."
So to guarantee the privacy of your data, set it up on your own server (maybe even locally hosted if you're that paranoid) and you're set.
From the README on Github:
"We provide a hosted version of this application on https://monicahq.com.
If you prefer to, you can simply clone the repository and set it up yourself on any hosting provider, for free. I'm just asking that you don't try to make money out of it yourself."
So to guarantee the privacy of your data, set it up on your own server (maybe even locally hosted if you're that paranoid) and you're set.