Trying to make donation matching counterfactual is manipulative behavior, in my opinion. People should be free to make donations to the charities that they think are best, rather than the ones that are the most donation-matched. If you want to convince people to donate to your favorite charity, just give an unconditional donation and tell other people that that's what you're doing and why you're doing it.
Why should we expect AI systems to develop bizarre and alien preferences when virtually all biological organisms have extremely normal preferences? (For instance, humans like to eat ice cream, but they don’t like to eat, as you mention, jet engine fuel.)
Isn't this backwards? We call eating ice cream normal because humans like to do it, not the other way around. That isn't evidence that AIs will have normal (i.e. similar to human) preferences.
I'm probably not competent to look at the details, but their paper sets off my BS detector by its reference to Godel's incompleteness theorem and its notion of "non-algorithmic understanding". These are both reminiscent of the Lucas-Penrose idea that consciousness requires uncomputability and that humans have some sort of magical ability to determine the truth-values of Godel sentences. I think the conventional view, sometimes known as the Church-Turing thesis, is that the universe is in fact computable.
Re God deciding to establish a system of morality: Presumably this amounts to God making a bunch of moral claims, and then us defining "morality" as "the system of moral claims made by God". But I don't see why this system should have any definitive relationship with what we ordinarily talk about when we talk about "morality". After all, our usual talk of morality is intricately connected with how we plan what we are going to do -- we hopefully plan to do moral things. Now maybe we also plan to follow God's system of morality, either because we've decided to submit to his omnipotence or because we think his system of morality is a rather good one. But these are not necessary relations but rather practical or moral considerations. In other words, we follow God's will because God is moral (or we don't follow his will because he isn't moral), rather than morality being defined by God's will. This distinction is important to make in case we want to make sense of moral criticism of God for Old Testament atrocities or other possible moral failings of his, even if we believe in God.
So no, I don't think that God's existence would bear any relation on whether morality is objective.
Preventing abortion is more tractable than malaria prevention(which I would guess is likely true)
Huh, my guess would have been the opposite. To prevent an abortion, you have to actually convince someone to do something they didn't want to do (or advocate for political change to force them to do it), whereas people already don't want to die from malaria, they just need resources to help them do that. That said I really have no idea, you may be right.
I'm not a fan of non-counterfactual donation matching, but your proposal is making things worse, not better. You are basically holding hostage your donation to try to get other people to do what you want.
On the other hand, I like the idea of a long whitelist of charities, because then it is giving other people power. But I don't see any connection between that and your proposal; just say that if not all matching funds get distributed initially then they get distributed according to some distribution determined beforehand by the matching funder.