The Supreme Court on Monday rejected Google's appeal of the Google-Oracle API copyright dispute. The high court's move lets stand an appellate court's decision that application programming interfaces (APIs) are subject to copyright protections.

Here is how we described the issue in our earlier coverage:

The dispute centers on Google copying names, declarations, and header lines of the Java APIs in Android. Oracle filed suit, and in 2012, a San Francisco federal judge sided with Google. The judge ruled that the code in question could not be copyrighted. Oracle prevailed on appeal, however. A federal appeals court ruled that the "declaring code and the structure, sequence, and organization of the API packages are entitled to copyright protection." Google maintained that the code at issue is not entitled to copyright protection because it constitutes a "method of operation" or "system" that allows programs to communicate with one another.

The high court did not comment Monday about the case when announcing that it had decided against reviewing it. However, the court's announcement comes a month after the Justice Department sided with Oracle and told the justices that APIs are copyrightable (PDF).

Computer scientists had urged the Supreme Court to review the case, saying the appellate court's decision "poses a significant threat to the technology sector and to the public."

Despite the high court's inaction on the case, the Google-Oracle legal flap is far from resolved. That's because the appeals court sent the case back to the lower courts to determine whether Google's use of the code in Android—which it no longer uses—constitutes a "fair use." Oracle is seeking $1 billion in damages.

"This is not the end of the road for this case—the Federal Circuit decision explicitly left open the possibility that the kinds of uses Google made were permissible under copyright's fair use doctrine," said Charles Duan, the director of Public Knowledge's patent reform project.

What is fair use? The US Copyright Office says that defense to copyright infringement is decided on a case-by-case basis. "The distinction between what is fair use and what is infringement in a particular case will not always be clear or easily defined. There is no specific number of words, lines, or notes that may safely be taken without permission. Acknowledging the source of the copyrighted material does not substitute for obtaining permission," the US Copyright Office says.

In a statement, Google said it would "continue to defend the interoperability that has fostered innovation and competition in the software industry." Oracle, however, countered, saying the outcome is a "win for innovation."