BCL vs GPL
"The current version of Java - Java SE 8 - is free and available for redistribution for general purpose computing. Java SE continues to be available under the Oracle Binary Code License (BCL) free of charge. JRE use for embedded devices and other computing environments may require a license fee from Oracle. Read more about embedded use of Java SE or contact your local Oracle sales representative to obtain a license. "
However, Sun released the source code of the Class library under GPL on May 8, 2007, except some limited parts that were licensed by Sun from 3rd parties who did not want their code to be released under a free software and open-source license.
So if the Android platform uses Java SE or some derivative under the older GPL then it's fine otherwise if they used the BCL version of Java then pay a licence?