WASHINGTON—A federal appeals court revived Oracle Corp.’s multibillion-dollar copyright infringement claims against Alphabet Inc.’s Google, in a ruling that could give fresh legal muscle to leading software makers but hamper upstarts developing new applications for computers and smartphones.

The court ruled Tuesday that Google’s use of Oracle’s Java programming technology wasn’t “fair,” a reversal of fortune in a case that dates back to 2010, when Oracle alleged Google’s Android smartphone operating system infringed copyrights...