Not to be confused with the GPL linking exception.

GNU Classpath is a project aiming to create a free software implementation of the standard class library for the Java programming language. Despite the massive size of the library to be created, the majority of the task is already done, including Swing, CORBA, and other major parts. The Classpath developers have implemented almost all of the classes from J2SE 1.4 and 5.0. Classpath can thus be used to run popular Java-based software such as Vuze and Eclipse.