The ruling actually goes beyond jb / unlocking, to include some cases of ebook text-to-speech, software protected by hardware dongles, video game testing and DVD ripping.
From
http://www.copyright.gov/1201/ :
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.
(1) Motion pictures on DVDs that are lawfully made and acquired and that are protected by the Content Scrambling System when circumvention is accomplished solely in order to accomplish the incorporation of short portions of motion pictures into new works for the purpose of criticism or comment, and where the person engaging in circumvention believes and has reasonable grounds for believing that circumvention is necessary to fulfill the purpose of the use in the following instances:
(i) Educational uses by college and university professors and by college and university film and media studies students;
(ii) Documentary filmmaking;
(iii) Noncommercial videos.
(2) 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.
(3) 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.
(4) Video games accessible on personal computers and protected by technological protection measures that control access to lawfully obtained works, when circumvention is accomplished solely for the purpose of good faith testing for, investigating, or correcting security flaws or vulnerabilities, if:
(i) The information derived from the security testing is used primarily to promote the security of the owner or operator of a computer, computer system, or computer network; and
(ii) The information derived from the security testing is used or maintained in a manner that does not facilitate copyright infringement or a violation of applicable law.
(5) Computer programs protected by dongles that prevent access due to malfunction or damage and which are obsolete. A dongle shall be considered obsolete if it is no longer manufactured or if a replacement or repair is no longer reasonably available in the commercial marketplace; and
(6) Literary works distributed in ebook format when all existing ebook editions of the work (including digital text editions made available by authorized entities) contain access controls that prevent the enabling either of the books read-aloud function or of screen readers that render the text into a specialized format.
