If you can't use their systems for a donation with a sales tax rate of 0%, then per the policy that means you can route users to alternative payment methods for those transactions. So by your reasoning, if donations to OSC are not subject to sales tax, then what the app is doing should be okay.

(As an aside, I have no idea if donations to OSC are subject to sales tax, but I would be surprised if they were given there is no sale or supply happening, and no one here seems to have suggested they are.)

> In any case, whether you think these are easier or harder, and regardless of which cases should be supported from a business perspective, their policy page (at least the one that I'm reading) very clearly says you can't use their system for such donations.

I disagree, because it uses the loose term "tax exempt donations", and nobody, it seems, can agree on whether that means exempt from income tax (ie, recipient does not need to pay income tax on it), exempt from sales tax, or deductible for income tax purposes (personally I think this is likely what it is intended to capture, and the only real basis on which to distinguish between 501(c)(3) and 501(c)(6) organisations, but in fact is the least supported by a literal reading).