Clarify licenses and describe them in the top-level README

* Fix URL to the GPL 2 with Classpath exception file.

compiler/README.md

@@ -96,3 +96,7 @@ You need to use the same JDK the [OTN](http://www.oracle.com/technetwork/oracle-
 The build step above should work on all [supported JDK 8 build platforms](https://wiki.openjdk.java.net/display/Build/Supported+Build+Platforms).
 It should also work on other platforms (such as Oracle Linux, CentOS and Fedora as described [here](http://mail.openjdk.java.net/pipermail/graal-dev/2015-December/004050.html)).
 If you run into build problems, send a message to the [Graal mailing list](http://mail.openjdk.java.net/mailman/listinfo/graal-dev).
+
+## License
+
+The Graal compiler is licensed under the [GPL 2](https://github.com/graalvm/graal/blob/master/compiler/LICENSE.md).

docs/README.md

@@ -1,4 +1,12 @@
 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](http://www.oracle.com/technetwork/oracle-labs/program-languages/overview/index.html).
 
-[Truffle](https://github.com/graalvm/graal/blob/master/truffle/README.md) 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](http://graalvm.github.io/graal).
+[Truffle](https://github.com/graalvm/graal/tree/master/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](http://graalvm.github.io/graal).
+
+[Graal](https://github.com/graalvm/graal/tree/master/compiler) is a dynamic compiler written in Java that integrates with the HotSpot JVM.
+
+## License
+
+[Truffle](https://github.com/graalvm/graal/tree/master/truffle) and its dependency [Graal SDK](https://github.com/graalvm/graal/tree/master/sdk) are licensed under the [GPL 2 with Classpath exception](https://github.com/graalvm/graal/blob/master/truffle/LICENSE.GPL.md).
+
+The [Graal compiler](https://github.com/graalvm/graal/tree/master/compiler) is licensed under the [GPL 2](https://github.com/graalvm/graal/blob/master/compiler/LICENSE.md).

truffle/README.md

@@ -124,5 +124,5 @@ Detailed info can be found in the [contributing document](CONTRIBUTING.md).
 
 ## License
 
-The Truffle framework is licensed under the [GPL 2 with Classpath exception](https://github.com/graalvm/truffle/blob/master/LICENSE.GPL.md).
+The Truffle framework is licensed under the [GPL 2 with Classpath exception](https://github.com/graalvm/graal/blob/master/truffle/LICENSE.GPL.md).
 The SimpleLanguage is licensed under the [Universal Permissive License (UPL)](http://opensource.org/licenses/UPL).