Beyond the information Apple provides to developers (provided you opt-in), Pipilo itself collects no information about you and refrains from logging how it is used.
When signing into Pipilo, it requests specific permissions from your Mastodon account, such as the ability to submit a post. This is very simply because in order for Pipilo to do anything Mastodon requests that you give the client the ability to do these things. Pipilo never performs any actions without you clearly requesting it to (such as by tapping a button). This is required in order for the app to function whatsoever.
Pipilo may link to external sites that are not operated by me. Please be aware that I have no control over the content and practices of these sites, and cannot accept responsibility or liability for their respective privacy policies.
If you have any questions or concerns regarding the above policy, you can contact me at firstname.lastname@example.org.