Android, since its humble beginnings, has always been an open source operating system, which means that anyone can grab the required information and source code free of any kind of charges. This openness has allowed numerous developers to create their own variants of the OS; including the incredibly popular stand alone Cyanogen OS. Android, was in its core, designed using Java; this means that Oracle itself has something to do with Google's own operating system. Java was first released in 1995 as a programming language, and was always completely free to use; until last year, when Oracle left victorious from a federal appeals' court ruling, which essentially allowed the company to copyright various parts of Java. Today, Google was denied by the Obama administration its appeal against the amount of copyright protection that Java could obtain after Oracle's federal appeal.
Google is greatly concerned about Java being partially copyrighted, as it will most likely change how developers all around the world use Android's source code to build their own variants of the operating system, leading to a halt on the amount innovation that Android could get. The company behind Android, quickly expressed how the Java programming language should be completely free to use, and started a case back in January against Oracle; in which Google communicated its disgust with how much copyright protection Java would obtain after last year's federal appeal, this made the fight between Oracle and Google much more tense, as Obama's administration responded negatively after the Supreme Court asked for its opinion about the Google-Oracle case.
The main reasoning behind Google wanting to avoid paying any fees to distribute Android is that they feel software developers' creativity and innovation would be essentially restricted. Oracle addressed Google's statement and said that well-implemented copyright protection would give developers more confidence when creating both applications and variants of the Android mobile operating system. U.S. Solicitor General Donald Verrilli ruled that Google's arguments against the copyright protection of Java lacked enough merit to be reviewed by the Supreme Court. That doesn't mean that Google's efforts were in vain, as Donald Verrilli also added that Java's copyright raised important concerns about software development, but said concerns could only be addressed through a "fair use" defense.