One is the non-reductionist metaphysical doctrine that the normative is sui generis and unanalysable into non-normative components or in purely non-normative terms, leading some writers to classify views as forms of ‘non-naturalism’ on this basis.

means Moore thinks you can't reduce 'ought' claims to 'is' claims, roughly.

The other legacy is the epistemological doctrine of intuitionism: that some substantive or synthetic normative truths are knowable a priori.

means that Moore thinks that you have access to informative moral truths (like 'it is wrong to kill wontonly' and not just 'murder is illegal homocide') in such a way that doesn't make reference to any particular experiences or contingent facts about the world. So Moore thinks that you can know 'it is wrong to kill wontonly'' independently of knowing any of the specific facts about human beings or human societies or anything like that.

But right, non-naturalism is a possibility for normative theories (and not a particularly unusual one, since all Kantians would count as non-naturalists). I'm not a non-naturalist myself, but I suspect cousin isn't getting away with eliminating the 'ought' in referring to utility functions, but just hiding it in the utility function. But I'm not well versed in that sort of thing, so I don't think I'm quite entitled to the criticism.