https://support.google.com/googleplay/android-developer/answ...
"Developers charging for apps and downloads from Google Play must use Google Play's billing system as the method of payment. Play-distributed apps must use Google Play's billing system as the method of payment if they require or accept payment for access to features or services, including any app functionality, digital content or goods."
https://support.google.com/googleplay/android-developer/answ...
Can you explain which of those categories this payment ("The app doesn't provide any special features to people who donate; it's just a way to help support the project.") falls under?