This legal theory, if true, destroys the DAO. Because the loophole in the contract wasn't fine print that nobody read, it was the entire premise upon which the contract was signed : The code IS the contract, and nothing else. If the contract now has to be enforced in court by human judges the entire DAO is worthless, and nobody should give it any respect whatsoever.
If the code is the contract, then the loophole that allowed the DAO to be drained is even more hidden than a note in the fine print: the plain code of the contract would appear to forbid it, and really careful consideration of how the code interacts with Etherium as a whole is required to spot the problem. (Even the Etherium team themselves may have missed it.)
That doesn't really save the DAO. As soon as it's open to interpretation (by human beings) whether part of the DAO is a bug or not, the point of algorithmic contracts are moot. Why not just stick with a traditional, human interpreted contract if it will come down to human decisions anyway? Your contract now has to read something like "By the way, this code is probably correct, but if there is a mistake, we have to litigate it in a human court." What is the point of the DAO now? You can get that with traditional investment instruments.
Would DAO:s then require to be released together with mathematical proofs [0], for the creators to be free from responsibility?
[0] Assuming they'd be clearly enough defined, where the proven mathematical statements have a meaningful and useful correspondence to the marketing statements.