Actually the proper command for running LimeWire should be
java -jar /Applications/LimeWire/RunLime.jar

The problem is not caused by LimeWire's java code, but either by the run script or MacOSX' WindowManager, that does not properly handle the command to start the java app.

Since the WindowManager is the task that uses 70%-80% of the cpu resources I assume this is a MacOSX bug.