Google’s copying of the Java SE API, which included only those lines of code that were needed to allow programmers to put their accrued talents to work in a new and transformative program, was a fair use of that material as a matter of law. Six holdings: fair use question was mixed question of fact and law, for purposes of standard for appellate review; Seventh Amendment right of trial by jury does not include fair use defense; assuming copyrightability, nature of copyrighted work was factor weighing in favor of finding fair use; transformative purpose and character of use constituted factor weighing in favor of finding fair use; amount and substantiality of portion used constituted factor weighing in favor of finding fair use; and market effects constituted factor weighing in favor of finding fair use.