Specify that Java is gratis

Technically, it is open-source: see http://openjdk.java.net/
There are various proprietary closed modules included to OpenJDK that
make it Oracle JDK, however.

Downloading and installing this cask means that you agree to the terms
of Oracle Binary Code License Agreement:

http://www.oracle.com/technetwork/java/javase/terms/license/index.html