Important to note here that most large individual contributions are made through a DAF or donor-advised fund, which counts as a public source in the support test. This helps donors maximize their tax incentives and prevents the charity from tipping into private foundation status.

Their IRS determination letter says they are formed as a public charity and their 990s claim that they have met the "public support" test as a public charity. But there are some questions since over half of their support ($70 million) is identified as "other income" without the required explanation as to the "nature and source" of that income. Would not pass an IRS audit.

> Nothing about 501(c)(3) entails providing any sort of good or service to society at large.

Sure it does:

https://www.irs.gov/charities-non-profits/charitable-organiz...

> Nothing about 501(c)(3) entails providing any sort of good or service to society at large.

While one might disagree that the particular subcategories into which a 501c3 must fit into one of do, in fact, provide a good or service to society at large, that's the rationale for 501c3 and its categories. Its true that "charity" or "charitable organization" (and "charitable purpose"), the common terms (used even by the IRS) is pedantically incomplete, since the actual purpose part of the requirement in the statute is "organized and operated exclusively for religious, charitable, scientific, testing for public safety, literary, or educational purposes, or to foster national or international amateur sports competition (but only if no part of its activities involve the provision of athletic facilities or equipment), or for the prevention of cruelty to children or animals", but, yeah, it does require something which policymakers have judged to be a good or service that benefits society at large.