Oracle has raised questions whether a version of Google's Android operating system running OpenJDK code will at all get an open-source license.

Google told a court in California that it released on Dec. 24 new versions of its Android platform that are licensed for use under a free, open source license provided by Oracle as part of its OpenJDK project, a redesign that apparently aims to get around charges that the previous versions of Android infringed Oracle's copyrights on Java.

OpenJDK is the open-source implementation of the Java Platform, Standard Edition.

Oracle contests that the December release of files by Google does not tally with the search giant's regular procedure for new releases. "Quietly posting a working copy of code is not how Google announces new versions of Android," it said in a filing. The code for the new versions were made available on the Android Open Source Project repository.

The focus of the lawsuit has narrowed down to 37 Java APIs (application programming interfaces), which were said to have been infringed by Google in Android.

While stating that it would like the trial on May 9 to be limited to versions of Android up to Marshmallow, Oracle said that the publication on Christmas Eve of some files "does not affect the 1.5 billion Android devices in active use through the end of 2015 based on Android versions through Marshmallow."

Oracle said that Google’s new defense at a late stage would prejudice the software company, as "the suggestion of a future license would be highly misleading and confusing to the jury, which might believe that such a license excused past infringement."

"Even assuming that a future version of Android will include OpenJDK code, there is no way to know whether that version will actually be entitled to the protection of the applicable licenses," an Oracle attorney wrote in a filing Tuesday. "Discovery will be required to determine how the OpenJDK code relates to and interacts with non-OpenJDK code used in Android, the compatibility (or lack thereof) of the licenses included in the new Android version, the license terms attaching to the entire platform, and Google’s (and others’) compliance with those terms," according to the filing.

"This is assuming a commercial actor who infringed for nearly a decade can claim the benefit of those licenses at all," the filing added.

Judge William Alsup of the U.S. District Court for the Northern District of California, San Francisco division ruled in 2012 that the APIs were not copyrightable. This decision was overturned in 2014 by the Court of Appeals for the Federal Circuit, which ruled that the Java API packages can be copyrighted. Google then appealed to the Supreme Court, which referred the case back to the district court for a decision on whether Google’s use could be seen as fair use.