CultofMac reports, that the US Copyright office has issued a new set of exemptions to the DMCA, making jailbreaking and unlocking your iPhone officially legal.

Here are the two exemptions as they specifically apply to jailbreakers, quoted from the official record:

The Librarian of Congress has announced the classes of works subject to the exemption from the prohibition against circumvention of technological measures that control access to copyrighted works. Persons making noninfringing uses of the following six classes of works will not be subject to the prohibition against circumventing access controls (17 U.S.C. § 1201(a)(1)) until the conclusion of the next rulemaking…

Computer programs that enable wireless telephone handsets to execute software applications, where circumvention is accomplished for the sole purpose of enabling interoperability of such applications, when they have been lawfully obtained, with computer programs on the telephone handset….

Computer programs, in the form of firmware or software, that enable used wireless telephone handsets to connect to a wireless telecommunications network, when circumvention is initiated by the owner of the copy of the computer program solely in order to connect to a wireless telecommunications network and access to the network is authorized by the operator of the network.

In other words, it is now okay to jailbreak your iPhone to run legally acquired software (for example, through Cydia) and to unlock your iPhone to run on another network.