In association with GraalVM, Oracle developed a language abstract syntax tree interpreter called Truffle which would allow it to implement languages on top of the Graal framework - wikipedia

The Truffle framework was released under GNU General Public License with the classpath exception to encourage use of the framework for projects which do not want to be bound by the viral license, copyleft nature of the GPL, while the Graal compiler remains under GPLv2 only.

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