Kanbann was created by Atadore, a Swiss company.
Atadore does not collect or store any data on its servers when you use the app. Nor does the app use third party services for analytics, advertising etc.
This app DOES send your data to Trello’s servers. The Trello privacy page is here
In brief, this app does not send data to Atadore’s servers when you are using it, nor to services other than Trello’s.
When logging in, you are briefly connected to an Atadore server to help login to your Trello account. This is a transient process and all your data is deleted from this server within five minutes, or as soon as you complete the login, whichever comes first.
This app is in no way associated with Trello.