Google is on the hook for billions of dollars in damages after a federal appeals court decided that it violated Oracle’s copyright by using Java code in its Android operating system. The case has been sent down to a lower-level court for damages to be calculated, but if Oracle gets its way, Google will be paying several billion dollars in damages.

More worryingly, however, the lawsuit sets a strict precedent on the use of application program interfaces (APIs) in coding. The tech community has been divided over the case, but critics are warning that a harsh verdict against Google will have a chilling effect on the speed of innovation in software.

APIs are pre-written chunks of code that provide a common framework for performing an action across all different types of devices. Oracle, the owner of Sun Microsystems, which first developed the Java language in the 1990s, has its own set of APIs for its own proprietary Java implementation, Java Standard Edition. Google’s Android operating system is written in a different (but very similar) implementation of Java, and it has its own APIs. The lawsuit centers around whether Google’s APIs, which are technically different but functionally identical to Oracle’s, breach the copyright.

Unfortunately for Google, the Federal Circuit court ruled in 2014 that APIs are copyrightable, a decision that set the stage for Oracle’s win in court today. Google was trying to argue that its use of Oracle’s APIs were “fair use,” as Oracle allows for non-commercial use, or for its software to be used in the development of other applications. What it doesn’t allow for is its technology to be embedded into a competing platform, which is what the Android operating system is.

“The fact that Android is free of charge does not make Google’s use of the Java API packages noncommercial,” the Federal Circuit ruling said, noting also that Google collects significant advertising revenue from Android.

Mozilla, the developer of Firefox, filed an amicus brief siding with Google in the case. “In order for open source to thrive, programmers need to reuse and reimplement existing Application Programming Interfaces (APIs) – the technical standards according to which computer programs interoperate with each other. Without such interoperability, open source programs lose much of their value as creative and competitive alternatives to proprietary – or “closed source” – programs. By making the information needed for interoperability available to all and thereby making the choice to switch software both cost-effective and frictionless, APIs ensure that consumers have open source alternatives to proprietary software,” the company said.