The java JDK is currently open source under the SCSL and JRL licence. You can get the download form here if you are interested:
http://www.sun.com/software/communit...2/download.xml
It looks like they are opening up the whole system now. I dont think they have announced what license they are going to use, but i doubt it will be the GPL. If its not the GPL then dont expect the major linux distros to come with it as they are sill of the opinion to only include GPL or GPL compatible code. You can thank Richard Stallman and the FSF for that.
I dont really see there being much of an advantage to being able to see the internals of java. The problem with projects like this is you can get tainted by the source and my find it hard to work on other similar open source projects for fear of copying concepts or even code from java into them. It is sounding more like the gresture MS gave when it released a version of .net called rotor or Shared Source CLI under their shared source licence. These style of licenses are very restictive and are really only useful for academic purposes. I wonder if this release will coincide with the release of Java 1.6.
Edit:- Slashdot article for those who like to read some (educated) arguments:
http://developers.slashdot.org/devel.../1550251.shtml