Why do you say the practical impact of the Copyright Office's decision is limited?
Until this week, Apple has possessed the legal equivalent of a double-barreled shotgun, which would have permitted the company to file lawsuits accusing users (or jailbreak software creators) of violating both the DMCA and breaching the contract in the form of the Apple iPhone Software License Agreement.
Now, thanks to the Copyright Office, Apple's legal arsenal has been reduced to a single-barreled shotgun, the license agreement.
But these amount to legal claims that the company could
in theory pursue. In reality, Apple has never sued a single person for jailbreaking or distributing jailbreaking software. It's never even threatened to do so, even after years have elapsed.
Translated: If Apple isn't going to sue the hundreds of thousands of customers merrily jailbreaking their iPhones, or the active developer community abetting their theoretically illicit activities, it doesn't matter what the caliber of their legal weaponry is.