While I agree that the likelihood of successfully suing the Ethereum Foundation is extremely remote, I think what has been missed is that this isn't "just" software. There IS no EULA.
There is a perception that a smart contract on the blockchain should be inviolable - it is what it is and requires no further clarification or qualification. It is irreversible. If this is accepted, then if the contract can be made to behave in an unexpected way then it can be argued that this is still within the coded intent of the contract. This seems to be the stance of the "attacker". Writing code to interact with contracts and the ethereum blockchain is part of its core functionality, which raises questions regarding "normal use" vs the "code injection" claim.
Some are claiming that only a mining consensus is required to hard-fork the funds back into the DAO because they believe that the redirection of the funds to a child DAO is an illegal hack.
The latter approach may destroy any trust in future smart contracts and the coin's blockchain as a whole (for others it may reassure them much like a bank's abilities to reverse transactions reassures). The former case of a flaw in the contract comes at a loss for investors (30-40%) which they feel it is necessary to recover (via a hard/soft fork). I can see both sides of the argument.
Regardless of who is right or wrong this whole event raises some serious questions regarding the reliability and usefulness (in non-trivial applications) of Ethereum smart contracts. Proposing a hard fork to "fix" a transaction seems to me to be a poor answer to the problem. Shooting the person who caught you with your pants down is likely to be seen as inappropriate.....
As an academic example I find it fascinating. Attitudes and behaviours of the actors involved is also extremely interesting. There is now also talk of a bounty for miners to influence their choice of node version to run. "Buying consensus" could be coming to a blockchain near you.... soon.
I don't own any DAO. I did not invest (an ICO using funds from an ICO just seemed a step too far for me). I mine Ethereum for profit amongst other coins. I may feel less impartial had I invested a significant sum in DAO!