Java Virtual Machine - Licensing

Licensing

Starting with Java Platform, Standard Edition (J2SE) 5.0, changes to the JVM specification have been developed under the Java Community Process as JSR 924. As of 2006, changes to specification to support changes proposed to the class file format (JSR 202) are being done as a maintenance release of JSR 924. The specification for the JVM is published in book form, known as blue book. The preface states:

We intend that this specification should sufficiently document the Java Virtual Machine to make possible compatible clean-room implementations. Oracle provides tests that verify the proper operation of implementations of the Java Virtual Machine.

Oracle's JVM is named HotSpot. Clean-room Java implementations include Kaffe and IBM J9. Oracle retains control over the Java trademark, which it uses to certify implementation suites as fully compatible with Oracle's specification.