It would be very nice to have a portable version of the Java Development Kit or the Java Runtime Environment/Java Virtual Machine made. Then we would finally have a solution for all of these Java problems (it would also open new doors in app development, like some I am exploring).
The source code for the JDK/JRE/JVM (i think the JDK) has been released. To my knowledge it is called Open JDK and is a developer/open source project to improve Sun's Java binaries.
Source Repositories: http://hg.openjdk.java.net/
Source Snapshots: http://download.java.net/jdk6/6u3/promoted/b05/index.html