Well, via obsfucators i am sure you can reduce the size of the JAR however you will probably have to combine your game and JOGL jar into one large JAR otherwise i imagine the obsfucators will either be unable to change method names/signatures or will do so such that your game will not be able to locate expected methods in the Jogl jar.

Another posibility seperate or combined with obsfucation is to use PACK200 to compress your JAR and use a launching class which unpacks and adds the JAR to the classpath at runtime.