The 501(c)(6) in question is Open Source Collective, which is a “business league or industry association” dedicated to providing financial and administrative assistance to Open Source projects. Anki does not have lawyers, Open Source Collective does.

https://oscollective.org

This is an interesting rabbit hole if you bother to go down it, I encourage you to do some more research.

Since you seem to have done the research, can you link some other iOS or Android apps that have been allowed to solicit donations for the Open Source Collective? Thanks.

I mean, come on. Just read their page. They're not a charity, at all. They're a "fiscal host" (which is a weird term right out of the gate) designed to solicit donations on behalf of other projects. They're literally a payment processor in competition with Google and Apple, and taking a cut of their own.

I mean, fine. They can do that. But that's not charity.