An appeals court on Friday breathed new life into Oracle's big-money lawsuit against Google by ruling that software commands can be copyrighted just like classic books.

A panel of three judges in the US Federal Circuit Court of Appeals concluded that a trial court erred last year by deciding Oracle application programming interfaces, referred to as APIs, are not entitled to the kind of copyright protection given to literature.

The panel maintained that it is bound to afford APIs protection under copyright laws "until either the Supreme Court or Congress tells us otherwise."

Champions of Internet freedom decried the appeals court ruling as a threat to innovation because it heralded an explosion in legal battles over software spreading beyond patents to copyrights in how code is written.

"We're disappointed-and worried," the Electronic Frontier Foundation (EFF) said in a blog post about the appeals court decision.

"The implications of this decision are significant, and dangerous."

- Unusual legal tactic -

Oracle's challenge of Google in court over copyrights was an unusual tactic being watched intently in Silicon Valley.

"We are extremely pleased that the Federal Circuit denied Google's attempt to drastically limit copyright protection for computer code," Oracle general counsel Dorian Daley said in an email response to an AFP inquiry.

Daley depicted the appeals court decision as "a win for Oracle and the entire software industry that relies on copyright protection to fuel innovation and ensure that developers are rewarded for their breakthroughs."

The appeal stemmed from a trial in 2012 before US District Court Judge William Alsup that ended Google being cleared of patent and copyright abuse charges leveled California business software titan Oracle.

Oracle argued that it held copyrights to how the APIs worked even if different strings of code were used to orchestrate the tasks.

In the fast-paced land of Internet innovation, it has been common for software writers to put their own spins on APIs that mini-programs use to "talk" to one another

- Fair use -

"When there is only one way to express an idea or function, then everyone is free to do so and no one can monopolize that expression," Alsup said in his ruling.

"So long as the specific code used to implement a method is different, anyone is free under the Copyright Act to write his or her own code to carry out exactly the same function or specification of any methods used in the Java API."

The appellate judges disagreed on the point and sent the case back to Alsup.

Google could appeal to the full appeals court panel and even pursue it to the US Supreme Court.

Appeals judges indicated in their ruling that Google might prevail on the legal grounds that "fair use" made it acceptable.

"Google can focus on asserting its fair use defense, and hope that fair use can once again bear the increasing burden of ensuring that copyright spurs, rather than impedes, innovation," the EFF said.

"We're confident that it can, but it shouldn't have to."

Oracle accused Google of infringing on Java computer programming language patents and copyrights Oracle obtained when it bought Java inventor Sun Microsystems in a $7.4 billion deal in 2009.

Google denied the claims and said it believes mobile phone makers and other users of its open-source Android operating system are entitled to use the Java technology in dispute.

Google unveiled the free Android operating system two years before Oracle bought Sun.

Oracle had been seeking billions of dollars in damages from Google based on copyright and patent claims.

The outcome of the trial left Oracle eligible for a relative pittance in damages based jurors finding that it misused nine lines of Java code in Android in an inconsequential win for Oracle.