OpenJDK is the open source reference implementation of the Java Standard Edition platform. The implementation is the upstream codebase from which Oracle builds the Oracle Java SE distribution. The two distributions are functionally and binary compatible at the major version level. OpenJDK is therefore the principal alternative to the Oracle Java SE Universal Subscription for buyers that want to remove the Oracle Java commercial exposure. The migration is technically straightforward in most cases. The migration also requires attention to the support model, to the version selection, and to the deployment patterns that depend on Oracle specific behaviour.
The OpenJDK project.
The OpenJDK project is hosted by the Java Community and is governed under the Oracle Contributor Agreement. Oracle is the principal contributor to the upstream codebase. Other contributors include Red Hat, Amazon, Microsoft, Azul Systems, and the broader Java community. The project produces the reference implementation that defines the Java specification.
The OpenJDK source code is published under the GPL with the classpath exception. The licence permits use in commercial and non commercial environments without a per use commercial fee. The licence does not include warranties or support obligations. The support obligation is provided separately by the distribution vendor or by a third party support provider.
The distribution options.
The OpenJDK source code is compiled into multiple distributions by multiple vendors. The principal distributions include Eclipse Temurin from the Adoptium project, Amazon Corretto from Amazon Web Services, Microsoft Build of OpenJDK, Azul Zulu from Azul Systems, and Red Hat OpenJDK. Each distribution is binary compatible with the OpenJDK reference at the major version level. The distributions differ in the support model, the long term support window, and the platform coverage.
The selection of the distribution should be driven by the support model rather than by the binary characteristics. A buyer that requires vendor support should select a distribution from a vendor that offers a commercial support agreement on the buyer estate. A buyer that does not require vendor support can select the Adoptium distribution which is the community supported reference distribution. See the Eclipse Temurin migration note for the detailed pattern.
The compatibility position.
The binary compatibility between Oracle Java and OpenJDK is established at the major version level. A Java application that runs on Oracle Java 17 will run on OpenJDK 17 without code change in the vast majority of cases. The exceptions are limited to applications that depend on Oracle specific features that are not part of the OpenJDK reference. The Oracle specific features include some commercial only options in older Java versions and some monitoring features in older releases.
The compatibility position should be tested on the actual application portfolio before the migration. The test plan should cover the principal applications in the production environment and should include functional testing, performance testing, and regression testing. The test plan should be completed in a non production environment that mirrors the production version of the Java runtime.
The version selection.
The version selection in the OpenJDK migration should align with the long term support release cycle. The OpenJDK long term support versions are released approximately every two years. The current long term support versions at the time of writing are version 17, version 21, and the upcoming version 25. Each long term support version receives security updates for at least five years from release.
The migration should target the most recent long term support version that the application portfolio supports. The selection of the most recent long term support version extends the support window and reduces the frequency of future major version migrations. A buyer that is on Oracle Java 8 should consider migration to OpenJDK 21 rather than to OpenJDK 8 even though the version 8 migration is technically smaller. The larger migration produces a longer runway.
The commercial saving.
The commercial saving from the OpenJDK migration is the elimination of the Oracle Java SE Universal Subscription. The Universal Subscription is priced per employee per month on the buyer global headcount. The annual cost can range from one hundred thousand dollars for a small organisation to several million dollars for a large organisation. The full annual cost is eliminated by the OpenJDK migration.
The commercial saving should be netted against the migration cost and against any third party support cost on the OpenJDK distribution. The migration cost is typically a one off project cost. The third party support cost is typically a fraction of the Oracle subscription cost. The net saving is usually substantial and is realised in the first year. See the Java licensing pillar for the broader Java commercial context.
The supportability question.
The supportability question is the principal concern that the Oracle account team raises in the migration conversation. The Oracle position is that the Oracle Java distribution is the only supported Java for enterprise use. The position is commercially motivated rather than technically grounded. The OpenJDK distributions are supported by their respective vendors and by third party support providers. The support coverage is comparable to the Oracle support coverage at a lower cost.
The buyer position should engage with the supportability question by selecting a distribution with a credible support model rather than by relying on community support alone. The credible support model gives the buyer a documented support path and removes the principal objection from the internal stakeholders.
Engaging an independent advisor.
The OpenJDK migration benefits from external review on the commercial and technical dimensions. An independent advisor can build the migration plan, the cost model, the distribution selection, and the support model on a coordinated track. The independent review also produces a defensible business case for the migration decision and supports the internal conversation with the stakeholders that have a preference for Oracle.
For the wider cluster see Java Licensing. For the service see Contract Review. For the deal structure see Java SE Universal. For the Oracle product see Oracle Java. For the full research read the Oracle Java Negotiation Guide.
A worked example.
A European financial services buyer migrated from Oracle Java 11 to Eclipse Temurin 21 in 2024. The buyer had approximately eight thousand employees and was facing an Oracle Java Universal Subscription cost of approximately one point three million dollars per year. The migration scope covered approximately six hundred Java applications in the production environment.
The migration was completed over a nine month period. The functional testing identified two applications that depended on a deprecated Oracle specific feature and required minor code changes. The third party support agreement with Azul Systems was structured at approximately one hundred and eighty thousand dollars per year. The net annual saving against the Oracle Universal Subscription was approximately one point one million dollars. The migration cost was recovered within four months of completion.