Long story short: we do not use your data in any way that isn't absolutely required by any app feature. Munin for Android does not (and won't ever) gather any personal information in any way.
Munin for Android is an open-source application: you can browse its code an execute it on your device from GitHub, on the following URL: https://github.com/chteuchteu/Munin-for-Android.
Note: Munin for Android relies on the following projects. Some of these (web APIs for example) are hosted on my own server, but you can host them yourself on your own. Their source code is also open-source, hence available for review.
Here are the permissions required by Munin for Android to work:
You can read the full permissions list from Munin for Android's
AndroidManifest.xml on GitHub.
We do not collect any information that may identify you, or any other personal data through these services. Since Munin for Android is an open-source application, you could clone its source code, get rid of these services and use it as-is if any of these ones bothers you.