Since retired, this modular Java runtime was one of Apache’s most controversial projects, sparking a dispute between Apache and Sun that carried over to Oracle’s stewardship of Java.
“The main goal of Harmony was to create a free and open source implementation of the Java runtime environment,” says Apache participant Jim Jagielski. “The project was retired due to Sun and then Oracle's refusal to grant Apache the required TCKs [Technology Compatibility Kits] to validate Harmony as Java-compliant, despite promises, guarantees, and signed contracts to do so.”
A field of use restriction imposed by Sun prevented Harmony’s use on mobile platforms, which Sun claimed would impact Java ME sales. Harmony, though, forced Oracle to accept OpenJDK and is a core component of Google Android, adds Jagielski.