It is now clear that jailbreaking your iPhone is legal, at least under the copyright law. Jailbreaking an iPhone is the process of opening up the software to allow the installation of applications other than those available through the official iTunes App Store. The EFF won the decision from the Copyright Office and the Librarian of Congress.  Apple had argued that altering its software on the iPhone was a violation of Apple’s software copyright. It is not. This process is also now legal on other handsets as well.

I don’t think this is actually a very big deal. Jailbreaking iPhones has been easy for some time and most people don’t bother. And it is true that jailbreaking and installing non-approved apps may make the phone less stable.

In any event, before you get too carried away by this new ability, be aware that Apple’s position remains that jailbreaking your iPhone voids it warranty. While it will not be a copyright violation, jailbreaking may be a contractual violation that causes the loss of warranty.

Update: And then there is this from Jon Zittrain, a Harvard Law professor:

The victory for those who want to hack is not trivial even though in large part it is symbolic. I mean here it is in honor of the United States government saying this is actually not illegal behavior, this is OK to jailbreak your phone. Interesting thing though is, the specific provision in title 17 of the US code is 1201 and this is 1201 (a)(1), that says you can’t hack in order to gain access to something protected by copyright. It turns out that there’s another provision that says you’re not allowed to market or traffic in tools whose primary purpose is to let people hack and the exceptions are not permitted to be applied to that provision. So even though the Library of Congress has given blessing to the act of hacking here. It’s not able to give a blessing to trafficking in the tools that let you hack.