OpenJDK

OpenJDK (Open Java Development Kit) is the free and open-source implementation of the Java Platform, Standard Edition, maintained by Oracle and a community of contributors. It serves as the reference implementation for the Java SE specification and the upstream source for most commercial JVM distributions, including Oracle JDK, Amazon Corretto, and Eclipse Temurin. The relationship between OpenJDK and commercial JDKs is often misunderstood: they are not competing products but different distributions of the same codebase, differentiated primarily by support contracts, release cadences, and bundled tooling.

The open-sourcing of the JDK in 2007 was not merely a licensing change. It was a strategic restructuring of the Java ecosystem's power dynamics. Before OpenJDK, the Java platform was controlled by a single vendor (Sun Microsystems, later Oracle). After OpenJDK, the platform became a commons — maintained collectively, forked commercially, and governed by the Java Community Process. The result is a rare example of a platform that survived the transition from proprietary control to open governance without fragmenting into incompatible variants.