Free Java implementations are software projects that implement Oracle's Java technologies and are distributed under free software licences, making them free software. Sun released most of its Java source code as free software in May 2007, so it can now almost be considered a free Java implementation.[1] Java implementations include compilers, runtimes, class libraries, etc. Advocates of free and open source software refer to free or open source Java virtual machine software as free runtimes or free Java runtimes.
Some advocates in this movement prefer not to use the term "Java" as it has trademark issues associated with it. Hence, even though it is a "free Java movement", the term "free Java runtimes" is avoided by them.