The Supreme Court has declined to hear Oracle v. Google, sending the long-running case back to a lower court where Google will have to argue that it made fair use of Oracle's copyrighted APIs. This has been a closely watched case, as the final decision could have a major impact on software development; a ruling in favor of Oracle, the Electronic Frontier Foundation says, could give certain tech firms "unprecedented and dangerous power" over developers by making it substantially more difficult for upstarts to create new software. That'll be the case unless fair use laws turn out to protect the use of APIs.

The case centers on the code behind Android. Google built Android on top of a modified version of Java, the programming language developed by Sun Microsystems (now owned by Oracle) in the ‘90s. To help spur the development of apps for its new platform, Google used Java's pre-existing APIs (Application Programming Interfaces), which many programmers were already comfortable using.

Fight over Android is all about the future of APIs

APIs are key to modern software development — they are bits of code that allow programs to communicate with each other. APIs are widely used today to allow third-party programs and services to build and expand on existing services. For example, third-party Twitter apps like Tweetbot use Twitter's APIs to pull in data from the social network. Many argue that the open use of APIs is central to the competition and innovation that has driven the software industry for years.

Oracle sued Google in 2010. The software giant argued that Google had infringed on its copyrights by using Java's APIs without permission. In defense, Google said that APIs can't be copyrighted. The principle, says Google, its that "open and interoperable computer languages form an essential basis for software development" and are key to "collaboration and innovation."

A district court ruled in Google's favor back in 2012, calling the API "a utilitarian and functional set of symbols" that couldn't be tied up by copyrights. Last May, a federal appeals court overturned that ruling by calling the Java API copyrightable. However, the court said that Google could still have lawfully used the APIs under fair use, sending the case back to a lower court to argue the issue. That's where Google will have to go next, now that the Supreme Court has declined to hear the issue over copyright itself.