The Microsoft Build of OpenJDK, explained for licensing.

When an enterprise decides to migrate off Oracle Java, the first practical question is which free distribution to move to. The Microsoft Build of OpenJDK is one of several no-cost, open-source OpenJDK distributions that answer that question. This guide explains what it is, how it is licensed, which Java versions it covers, and how it compares with the other free distributions — strictly from an Oracle Java licensing standpoint, because the reason to care about it is that it can take Oracle’s Java subscription bill to zero.

What the Microsoft Build of OpenJDK is

The Microsoft Build of OpenJDK is a free, open-source distribution of OpenJDK — the same upstream source code from which Oracle’s own JDK is built. It is one of a family of independent OpenJDK distributions that also includes Eclipse Temurin, Amazon Corretto and Azul Zulu. Each takes the OpenJDK source, compiles it, tests it for compatibility, and publishes ready-to-run binaries at no charge.

The important point for licensing is that “OpenJDK” is not a lesser version of Java. It is Java. The Java SE specification is implemented by OpenJDK, and Oracle’s commercial JDK is itself an OpenJDK build with a different licence and support contract attached. A distribution like the Microsoft Build of OpenJDK gives you the same language, the same APIs and the same runtime behaviour — without the Oracle subscription obligation.

How the Microsoft Build of OpenJDK is licensed

The Microsoft Build of OpenJDK is published under the GNU General Public License version 2 with the Classpath Exception (GPLv2+CE) — the standard open-source licence of the OpenJDK project. This is the single most important fact about it from a cost perspective: GPLv2+CE permits free use in production, including commercial and internal business use, with no per-employee fee, no per-processor fee, and no subscription.

The Classpath Exception matters specifically because it means linking your application against the Java class libraries does not impose GPL obligations on your own code. In plain terms: you can run business applications on a GPLv2+CE OpenJDK distribution in production without your software becoming subject to the GPL. This is the same licensing model under which Eclipse Temurin, Amazon Corretto and Azul Zulu are distributed, and it is the legal foundation of every Oracle Java migration.

Which Java versions it covers

The Microsoft Build of OpenJDK focuses on the Long-Term Support (LTS) Java releases — the versions enterprises actually standardise on. In practice that means builds for Java 11, Java 17 and Java 21, published for the major operating systems and for both Intel/AMD and ARM processor architectures.

For a migration, the LTS focus is a feature, not a limitation. Most enterprise estates run on LTS versions precisely because they receive a long, predictable stream of updates. If your applications run on Oracle JDK 11, 17 or 21 today, an equivalent free build is available; if they run on an older or non-LTS Oracle version, the migration plan should also include a version upgrade, which is good practice regardless of distribution.

How it works as a migration target from Oracle Java

Because the Microsoft Build of OpenJDK compiles from the same OpenJDK source and passes the same compatibility verification, swapping it in for Oracle JDK is, for the overwhelming majority of applications, a configuration change rather than a code change. You install the new runtime, point your application or container image at it, and run your test suite.

The cases that need attention are the same ones that need attention with any OpenJDK distribution: applications that depended on commercial features once exclusive to Oracle JDK, or on tools removed from Java over successive releases. These are identified during the testing phase of a migration and are typically a small, finite list. The distribution choice does not change which applications need remediation — it only changes the support relationship around the runtime.

The support model — and where it differs from Oracle

The Microsoft Build of OpenJDK provides free binaries with security and bug-fix updates aligned to the OpenJDK quarterly update cycle. For many estates — particularly internal applications and development environments — free binaries with timely updates are entirely sufficient.

Where an enterprise needs a contractual support relationship with defined response times for business-critical systems, several OpenJDK vendors offer paid commercial support, and the migration plan should decide which systems, if any, warrant it. The key contrast with Oracle is structural: with Oracle Java SE the subscription is effectively mandatory to receive updates and is priced on total employee headcount; with OpenJDK distributions the binaries and updates are free, and commercial support — if you choose to buy it — is an optional add-on scoped to the systems that need it. That inversion is the entire financial case for migrating.

Choosing between the free distributions

Enterprises sometimes spend longer than necessary deciding between the Microsoft Build of OpenJDK, Eclipse Temurin, Amazon Corretto and Azul Zulu. Because all are GPLv2+CE OpenJDK builds that pass the same compatibility tests, the choice is not about Java correctness — it is about operational fit.

Sensible criteria are: which operating systems and processor architectures you need; whether you want a single distribution standardised across the whole estate; how the distribution’s update cadence and packaging fit your patching process; and whether you intend to buy commercial support and from whom. Many enterprises standardise on one distribution for consistency and treat the others as interchangeable fallbacks. The decision is worth making deliberately, but it is not worth agonising over — and it should never become the reason a migration stalls.

The Oracle Java licensing takeaway

The reason the Microsoft Build of OpenJDK belongs in an Oracle Java licensing discussion at all is simple: it is one of the destinations that ends the Oracle subscription. Across 340+ Java licensing engagements, the enterprises that have eliminated Oracle Java cost did so by moving production workloads onto free GPLv2+CE OpenJDK distributions and then proving, with a clean re-scan, that no Oracle JDK remained.

Whichever free distribution you choose, the licensing logic is the same: free binaries, free production use, no employee-metric exposure, and — once the migration is validated — no Oracle Java audit risk, because there is no Oracle-licensable Java left to audit. The distribution is the tool; the licensing outcome is the prize.

Frequently asked questions

Is the Microsoft Build of OpenJDK free to use in production?

Yes. It is published under GPLv2 with the Classpath Exception, which permits free use in production, including commercial and internal business use, with no per-employee or per-processor fee.

Is the Microsoft Build of OpenJDK the same as Oracle Java?

It is built from the same OpenJDK source code and implements the same Java SE specification, so applications behave the same. What differs is the licence and the support model — it carries no Oracle subscription obligation.

Which Java versions does the Microsoft Build of OpenJDK support?

It focuses on the Long-Term Support releases — in practice Java 11, 17 and 21 — published for the major operating systems and processor architectures.

Will migrating to it remove our Oracle Java audit risk?

Once the migration is complete and validated, yes. With no Oracle JDK installed, there is no Oracle-licensable Java for Oracle to claim. The decommissioning and validation step is what makes this true.

How does it compare with Eclipse Temurin or Amazon Corretto?

All are free GPLv2+CE OpenJDK distributions that pass the same compatibility tests, so the choice is about operating-system support, update cadence and support preferences rather than Java correctness.

Conclusion

The Microsoft Build of OpenJDK is best understood not as a product to evaluate in isolation but as one of several free, equivalent destinations for an Oracle Java migration. It is the same Java, licensed under the open-source GPLv2 with Classpath Exception, with no per-employee fee and no subscription. For an enterprise weighed down by Oracle’s employee-metric pricing, the value is not in any single distribution’s feature list — it is in the licensing model they all share. Pick the free distribution that fits your operations, plan the migration properly, validate that no Oracle JDK remains, and the Oracle Java bill, and the audit risk that comes with it, simply ends.