AnkiDroid, a free and open-source flashcard app for Android, has been rejected by Google Play due to its donation link to Open Collective, a US non-profit organization with 501(c)(6) tax-exempt status. Google's policy states that apps may not lead users to a payment method other than Google Play's billing system, except for tax-exempt donations. AnkiDroid's developers are seeking clarification on whether their donation link complies with Google's policy. The app will be removed from Google Play on September 11 if the issue is not resolved.