GraalVM is a project based in Oracle Labs developing a new JIT Compiler and Polyglot Runtime for the JVM. Further details can be found on the OTN site.
Truffle is a framework for implementing languages as simple interpreters and forms the basis of the Polyglot Runtime. The official Truffle documentation is maintained as Truffle javadoc.
Graal is a dynamic compiler written in Java that integrates with the HotSpot JVM.
Substrate VM is a framework that allows ahead-of-time (AOT) compilation of Java applications under closed-world assumption into executable images or shared objects.
Truffle and its dependency Graal SDK are licensed under the GPL 2 with Classpath exception.
The Graal compiler is licensed under the GPL 2.
The Substrate VM is licensed under the GPL 2.