“Our app isn’t allowed to link to the homepage of the project’s own website unless we completely remove our users’ ability to discover a way to give us money.”
Language Transfer is free courses run by one man on donations. Google pulled the app because a reviewer clicked through the website twice and found a donate button with no 15% cut. Nonprofits get an exemption only if they are tax-exempt on paper. Google reinstated the app after the outcry. The policy is still there.