Yes, I don't think the terms should/would apply retroactively. But at least for new users he makes it clear that he'd like acknowledgment. Otherwise, he's just asking for this issue to happen again.
I'm not sure that he always wants acknowledgement, but he'd like it in this particular case.
For example, every comment I write on HN can be paraphrased freely by someone else--there's no contract saying you have to quote me directly. However, if my commentary---paraphrased or not---makes it onto the front-page of the New York Times then you can bet I'll be standing up in public and asking for a little recognition.
Consider this. He requested recognition, but did not demand it. They could have freely chosen to deny him recognition. That is a greater freedom to them, and we shouldn't gripe about it.
