Let me try. I am not a legal person.
I think there is a limit to the amount of gift in cash or other assets you can make without triggering a federal gift tax of around 40%. For an individual there is a limit of life time gift tax exemption around 11.5 million and 23 million if the gift is made as a couple.
1. A loan is a business transaction here. There is an expectation that it will be repaid. It can also be forgiven. A donation to a non profit can be ‘rewarded’ by way of tax deductions.
So Acton will profit from a similar tech he has already sold to Facebook as WhatsApp. His wealth likely came from WhatsApp sale to Facebook. It can be argued as conflict of interest.
Loan deals are very clean. Cut and dried. Any implied contract between the parties ends when the loan is repaid and the relationship is terminated.
2. I can’t speak for Acton. Or in any legal capacity, but if it were me, tax deductions to a non profit can be rife with complications because if he ever gets involved with signal as a board member or employee, it might rise questions.
3. Signal foundation is not a charity.
4. Even a billionaire ..and especially one..would prefer to keep books less complicated for IRS. Donations are often scrutinized for money laundering or tax evasion.
5. A gift invites taxes, iirc. Like..if I gifted you above 15k(and you are not my family or part of a trust/insurance beneficiary etc), you will have to pay taxes on the realized value of the gift.
6. This might have been an ideological instinct for Acton as there seems to have been some disagreement between Acton and FB on how they intended to take WhatsApp. Maybe this isn’t about money at all. Who knows. Hence the ‘Etc’.
Also I don’t know exactly what kind of non profit Signal is...