OpenJDK Uncovered: Oracle’s Plans, Licensing, and How to Contribute

Last week, with the release of Java 16, we published two articles about Java 16 and why many still use Java 8. Readers asked many questions about OpenJDK, so this article answers common OpenJDK questions and provides official answers.

About Open Source

What is Oracle’s plan for supporting Java open source?

Oracle intends to continue supporting open source and open standards, offering users choice, flexibility, and lower compute costs, without over‑emphasising the importance of open standards.

Does Oracle practice open‑source development?

Oracle leads or participates in many open‑source projects; see http://oss.oracle.com for details.

How can we learn more about Oracle’s view on open source and open standards?

Read the interview with Oracle chief architect Edward Screven at http://www.oracle.com/technetwork/oramag/2010/o40interview-086226.html .

Oracle’s Plans for OpenJDK

What does Oracle plan for the OpenJDK community?

Oracle will continue developing the next Java SE version together with the Java community; OpenJDK is the only open‑source Java SE implementation Oracle plans to participate in.

Is Oracle committed to OpenJDK?

Yes, Oracle remains committed to improving OpenJDK and welcomes external contributors.

Can you detail Oracle’s OpenJDK roadmap?

JavaOne 2010 accelerated Java SE availability with releases in 2011 and 2012; OpenJDK will serve as the basis for Oracle JDK 7 and JDK 8. More information is at http://blogs.oracle.com/henrik/2010/10/java_roadmap_from_javaone_2010.html .

What is JDK 7?

JDK 7 is Oracle’s implementation of the next Java SE platform; the OpenJDK JDK 7 project implements the features defined in the Java SE 7 JSR.

What will happen to JRockit? Will it become part of OpenJDK?

Oracle engineers are merging HotSpot and JRockit JVMs into a single product and plan to contribute the result to OpenJDK.

Will Oracle change the OpenJDK licensing model?

No. The GPL‑based licensing model has served the project well and will remain unchanged.

Is IBM joining OpenJDK?

Oracle and IBM announced in October 2010 a joint effort to develop a leading open‑source Java SE implementation, with OpenJDK as the primary development platform.

OpenJDK Users and Contributors

Who uses OpenJDK?

Major Linux distributions (Ubuntu, Fedora, RHEL) ship OpenJDK as the default Java SE implementation; a 2010 Eclipse survey showed 21 % of developers use OpenJDK, and many academic institutions base research on it.

Who contributes to OpenJDK?

Most contributors are engineers employed by companies such as Oracle, but academia, OS distribution developers, and individual developers also contribute.

Why does Oracle participate in OpenJDK?

Oracle uses an open‑source model to lower barriers to participation and attract the best ideas for Java development.

Does Oracle welcome new contributors?

Yes, but newcomers should subscribe to relevant mailing lists, study discussions, and start reviewing patches.

Compatibility

Will Oracle provide the Java SE 6 TCK to the OpenJDK community?

Access to the TCK is documented on the OpenJDK conformance site: http://openjdk.java.net/groups/conformance/JckAccess/index.html .

How to test an OpenJDK‑based implementation for Java SE compatibility?

Request access to the Java SE TCK from Oracle; if the implementation meets the OpenJDK TCK licensing terms, the JCK can be obtained under those conditions.

Is a list of organizations and individuals with Java SE 6 TCK access available?

Yes, see http://openjdk.java.net/groups/conformance/JckAccess/jck-access.html .

Can I build an open‑source distribution that fully satisfies Java SE 6 TCK requirements?

Yes; the first such build was based on the source released in the OpenJDK 6 project in 2008.

Contributing to OpenJDK

Will Oracle change how developers participate in OpenJDK?

No. The project will continue accepting contributions under the existing contributor agreement.

Should I discuss my ideas in the OpenJDK project?

Yes—find the most appropriate OpenJDK project and follow the contribution guidelines.

What are the conditions for joining OpenJDK mailing‑list discussions?

Subscribe to the relevant mailing list; participation is governed by the OpenJDK website terms of use.

Can non‑Oracle users contribute to OpenJDK?

Yes, under the same conditions as other contributors. See http://openjdk.org/contribute .

Can contributors discuss bug fixes and feature enhancements on the mailing lists?

Yes, Oracle welcomes everyone’s participation.

Licensing

What open‑source license does OpenJDK use?

GPL v2 for most of the VM, and GPL v2 with the Classpath Exception for libraries and public APIs.

How do I know which license applies to a given source file?

Each source file contains a copyright header indicating its license.

Why not use a different open‑source license?

The chosen license has served the project well, ensuring stable growth and minimizing proprietary forks.

Can I download the OpenJDK source code?

Yes, from http://download.java.net/openjdk/jdk6 and http://download.java.net/openjdk/jdk7 .

Are there any usage restrictions?

No; OpenJDK is released under a well‑known open‑source model that imposes no runtime restrictions.

Can I get legal advice on the OpenJDK mailing list?

Generally no; the mailing list is for technical discussion of OpenJDK development.

JDK 7 & JDK 8

Can features in OpenJDK builds be used in other Java SE implementations?

It depends on whether the feature is accepted by the Java Community Process and incorporated into the Java SE specification.

Is Java development frozen?

Absolutely not; Oracle engineers and the OpenJDK community are actively working on JDK 7 and JDK 8 projects such as Lambda and Jigsaw.

Will the Java language continue to evolve?

Yes; Oracle is investing heavily in language and platform improvements like Lambda, modules, and parallel libraries.

Can I experiment with new bytecode instructions using an OpenJDK build?

Yes; you can build OpenJDK binaries yourself or use the latest JDK 7 binary snapshots at http://dlc.sun.com.edgesuite.net/jdk7/binaries/ .

Can I rely on all features of a JDK 7 snapshot for production?

Not necessarily; snapshot features may not all make it into the final release and depend on developer feedback.

Oracle JDK and OpenJDK

Is Oracle JDK based on OpenJDK?

Yes; Oracle JDK is built from OpenJDK source code and adds closed‑source components.

What is a binary code license?

It is the license Sun (now Oracle) uses for the JDK and JRE; users must accept it before downloading.

How much does OpenJDK cost to download?

OpenJDK source code is provided under an open‑source license and is free of charge.

Does OpenJDK prevent other Java SE implementations?

No; users can choose from multiple compatible Java SE implementations offered by various vendors.