I have those two in the lib folder inside yuicompressor-2.4.2.zip. I ran the compressor completely fine without them. What are they for? Am I missing something?
Upon checking the dependency in yui source code it is clear that jargs class CmdLineParser is directly being used - and this dependency is also clear when one checks the ant build file lib path.
However, the lib folder is not used by the yui compressor jar itself - it is only used for compiling yui code. The actual yui compressor jar has all the contents of both the rhino and the jargs jar inside it - hence you can really just remove all the other contents of the folders and just use the yui compression jar directly.