Gnash stores only the information you explicitly choose to enter into the app. This includes things like your nicotine logs, reflections, and app settings that help Gnash function as intended.
That data exists solely so the app can work for you. Gnash does not collect usage analytics, crash analytics, advertising identifiers, location data, or any other information used for tracking, profiling, or marketing.
There are no hidden data flows and no background collection.