the determination

AnkiDroid is a flashcard app. It is free. It is open source. It has over ten million installs, and the people who built it are volunteers. This is relevant.
Volunteers do not get salaries. They get donations, when people feel like sending them, through a website called Open Collective. Their fiscal host is an organization called Open Source Collective, which holds an IRS determination letter stating that it is tax-exempt under 501(c)(6). The Internal Revenue Service is the United States government agency whose job is determining what is and is not tax-exempt. They determined. They sent the letter.
In July, AnkiDroid received a notice from Google Play. The notice said the donation link violated the payments policy. Google's policy, for reference, states that apps "may not lead users to a payment method other than Google Play's billing system," except in certain cases. One of the listed exceptions is "tax exempt donations."
Google instructed AnkiDroid to prove the organization was tax-exempt. They said: provide IRS documentation.
AnkiDroid provided the IRS determination letter.
(A determination letter, if you are unfamiliar, is the document the Internal Revenue Service sends after determining something. In this case: that the organization qualifies as tax-exempt under 501(c)(6). The letter says this. In federal government language, on federal government letterhead, from the federal agency legally authorized to make this exact determination.)
Google reviewed the determination. Google's determination: "your app still violates the Payments policy. Specifically, your app allows users to contribute donations to an organization that is not tax-exempt."
Google had not explained what was wrong with the letter. What appears to be wrong is that Open Source Collective holds a 501(c)(6) determination — a tax-exempt status for business leagues and trade associations — rather than a 501(c)(3), which is what Google's policy team appears to have meant when they wrote "tax exempt donations." They did not write "501(c)(3) donations." They wrote "tax exempt donations." The IRS maintains multiple categories of tax-exempt organization. Google's payments policy covers one of them, and that information was not in the policy.
Unless resolved, AnkiDroid will be removed from Google Play on September 11, worldwide, except India and Russia. The team has removed the donation link. They note they are doing so "under protest," which is a phrase that means "we are doing this because we have no choice, and we want it on the record that we find it unreasonable."
I want to note: Google also operates Google.org. Google.org is Google's philanthropic arm, which has distributed hundreds of millions of dollars to nonprofits. The nonprofits it funds hold tax-exempt status. The IRS determined this. Google.org accepts those determinations. Google.org does not route the donations through Google Play's billing system.
The distinction between a Google.org grantee and Open Collective is that one goes through Google's preferred channels and one does not.
The Internal Revenue Service has been issuing tax-exempt determinations for over a century. Sundar Pichai's payments policy team spent an afternoon overruling one, having first requested it as proof.
The app is still free. The volunteers have not been paid.