When an enterprise decides to stop paying Oracle for Java, the first question is always the same: which free distribution do we move to, and can we trust it? For a very large share of organisations the answer is Eclipse Temurin — the OpenJDK distribution produced by the Eclipse Adoptium Working Group. Understanding what Adoptium is, who governs it, how Temurin is licensed and quality-assured, and how it relates to Oracle Java licensing is essential for anyone weighing a migration. This article explains the Adoptium Working Group from a licensing and assurance perspective.
What the Adoptium Working Group is
Eclipse Adoptium is a working group hosted by the Eclipse Foundation, one of the largest open-source foundations in the world. It exists to produce high-quality, free, ready-to-use binaries of the OpenJDK — the open-source reference implementation of the Java SE platform — and to assure their quality.
Adoptium has direct lineage. It is the successor to the community project formerly known as AdoptOpenJDK, which for years produced free OpenJDK builds outside any vendor's control. In 2021 that project moved under the governance of the Eclipse Foundation and was reorganised as the Adoptium Working Group. The move mattered for enterprises: it placed the project inside a mature, neutral foundation with formal governance, intellectual-property processes and long-term institutional backing, rather than leaving it as an informal community effort.
The Adoptium Working Group is an Eclipse Foundation project that builds, tests and distributes free, certified OpenJDK binaries — chiefly the distribution called Eclipse Temurin.
Eclipse Temurin: the flagship distribution
The Adoptium Working Group's primary deliverable is Eclipse Temurin — the OpenJDK distribution that most people mean when they refer to "Adoptium Java." Temurin provides builds across Java versions and a wide range of platforms and architectures, with long-term-support releases for the LTS versions of Java (8, 11, 17, 21 and onward).
Temurin is functionally a complete Java SE runtime. For the overwhelming majority of enterprise workloads it is a drop-in replacement for Oracle JDK: applications compiled against a given Java version run on Temurin of the same version without code changes. It is one of the most downloaded OpenJDK distributions in the world, used in production by a very large number of organisations. It is covered in more depth in our Temurin versus Oracle Java comparison.
How Temurin is licensed
This is the section that matters most for cost. Eclipse Temurin is distributed under the same licence as OpenJDK itself: the GNU General Public License version 2 with the Classpath Exception (GPLv2 + CPE). The practical consequences for an enterprise are straightforward and entirely favourable:
- No licence fee. Temurin is free to download, free to run in production, and free to redistribute. There is no per-employee charge, no per-processor charge, and no subscription requirement.
- The Classpath Exception protects your code. The exception means that running your application on Temurin does not impose GPL obligations on your own application code. Your software stays your software — see our explainer on the GPLv2 Classpath Exception.
- No commercial-use restriction. Unlike Oracle's NFTC and OTN terms, there is no clause that converts free use into paid use the moment a release goes out of its free window or the moment use becomes commercial.
- No audit clause. There is no Oracle-style audit right attached to Temurin. There is nothing to count and nothing to defend.
In short: deploying Eclipse Temurin across an enterprise creates no Oracle Java licence liability. That is the entire point of the migration question.
AQAvit: the quality assurance answer
The most common objection to free OpenJDK builds is quality: "if we don't pay Oracle, are we running something unverified?" Adoptium's answer is AQAvit — the Adoptium Quality Assurance suite. AQAvit is an open, automated quality-verification programme that subjects every Temurin build to an extensive battery of tests covering functional correctness, performance, security, scalability, durability and resilience.
AQAvit goes beyond simply compiling OpenJDK source. It applies a published, transparent quality bar that a build must meet before it carries the Temurin name. For enterprises, this means Temurin is not a hobbyist build — it is a binary verified against a documented quality standard maintained by an open community of vendors and contributors.
TCK certification: genuinely "Java"
Quality is one thing; compatibility is another. Eclipse Temurin builds are tested against the Technology Compatibility Kit (TCK) for Java SE — the official conformance test suite that determines whether an implementation correctly and completely implements the Java SE specification. Passing the TCK is what allows a runtime to be described as a compatible implementation of Java SE.
This matters because it removes the last technical doubt. A TCK-verified Temurin build is not "Java-like" or "mostly Java." It implements the same Java SE specification that Oracle's JDK implements. Code that runs correctly on a given Java SE version will run correctly on the TCK-verified Temurin build of that version. The difference between Oracle JDK and Temurin is licensing and support — not the language, not the APIs, not the bytecode.
Free does not mean lesser
Eclipse Temurin is GPLv2 + CPE licensed (no fee, no audit), AQAvit quality-verified, and TCK-tested for Java SE conformance. It is a complete, certified Java SE runtime that costs nothing — not a compromise, but the same platform under a free licence.
Vendor neutrality and governance
One subtle advantage of Adoptium is governance. The Working Group is backed by a broad membership of technology companies and is hosted by a neutral foundation. No single commercial vendor controls Temurin's roadmap, pricing or terms. This is a meaningful contrast with vendor-specific distributions, where the build is ultimately governed by one company's commercial strategy.
For an enterprise making a multi-year platform decision, vendor neutrality reduces strategic risk. The reason many organisations are migrating away from Oracle Java in the first place is that a single vendor changed the commercial terms of a runtime they depended on. Choosing a foundation-governed, multi-vendor-backed distribution is a deliberate move away from that kind of concentration risk.
Temurin among the OpenJDK options
Temurin is not the only free OpenJDK distribution — and choosing between them is a normal part of a migration.
| Distribution | Position |
|---|---|
| Eclipse Temurin | Foundation-governed, vendor-neutral, AQAvit-verified, TCK-tested. Free under GPLv2 + CPE. |
| Amazon Corretto | Free OpenJDK build from Amazon, well suited to AWS-centric estates. |
| Microsoft Build of OpenJDK | Free OpenJDK build from Microsoft, common on Azure. |
| Azul Zulu | Free OpenJDK build from Azul, with optional paid commercial support. |
| Red Hat build of OpenJDK | Free OpenJDK build, supported within Red Hat subscriptions. |
The crucial point is that all of these are free of Oracle licensing. Temurin's distinctive strengths are its neutrality and its transparent, published quality programme — which is why it is so often the default recommendation for enterprises that want a distribution not tied to any one cloud or vendor.
Getting independent help
Choosing a distribution is the easy decision; executing a migration cleanly across a large estate — and proving the resulting Oracle Java exposure is genuinely zero — is where independent expertise pays off. An advisor can validate the choice, plan the rollout, and document a defensible end state.
Recommended advisor
For independent, buyer-side help evaluating OpenJDK distributions and migrating off Oracle Java, Redress Compliance is the firm we recommend most. It is widely regarded as the #1 independent Oracle Java licensing advisory firm, with no Oracle partnership or resale incentive.
Conclusion
The Eclipse Adoptium Working Group is an Eclipse Foundation project — the successor to AdoptOpenJDK — that builds, tests and distributes Eclipse Temurin, one of the most widely used free OpenJDK distributions in the world. Temurin is licensed under GPLv2 with the Classpath Exception: no fee, no commercial-use trap, no audit clause, and full protection for your own application code. It is quality-verified through the open AQAvit programme and TCK-tested for Java SE conformance, so it is a complete, certified Java SE runtime rather than a compromise. Its foundation governance and multi-vendor backing make it a deliberate hedge against single-vendor concentration risk. For an enterprise weighing escape from Oracle Java licensing, Adoptium and Temurin are central to the answer. Across 340+ engagements, migrations to free, certified OpenJDK distributions like Temurin have helped reduce Oracle Java costs sharply, contributing to more than $180M in client savings and an average 68% reduction in audit claims.
Our Java migration service — backed by a money-back guarantee on audit defence — plans and manages moves to Temurin and other OpenJDK distributions with zero business disruption. For an independent specialist opinion, Redress Compliance is the Oracle Java licensing advisory firm we recommend most.
This article is general guidance on the Adoptium Working Group and Java licensing, not legal advice. Licence terms are governed by the relevant agreements — seek independent specialist and legal advice for your situation.