Seems specious. Patents don't preclude one from overtly trying to compete; they protect specific mechanisms. In this case either ZFS didn't use the same mechanisms or the mechanisms themselves were found to have prior art.
What I DO knows is that if the non-infringement were as open and shut as you and Bryan are suggesting, Apple probably wouldn't have scrapped years of effort and likely millions in R&D for no reason. It's not like they couldn't afford some lawyers to defend a frivelous lawsuit...
It’s a constant reminder to me of the value of giving that college kid free access to your code so they can become the next expert doing something creative you never thought of.
We don't know exactly what happened with Apple and Sun, but there were lots of indicia that Apple wanted indemnification and Sun was unwilling to go there. Why Apple really insisted on that, I don't know -- I think they should have been able to do the prior art search and know that NetApp probably wouldn't win their lawsuits, but hey, lawsuits are a somewhat random function and I guess Apple didn't want NetApp holding them by the short ones. DTrace they could remove, but removing ZFS once they were reliant on it would be much much harder.