Uh yes, you will not be able to use LW 5. Only OSX 10.5 or later has Java 1.6. And only the intel computers made within past two years have ability to run Java 1.6 because Mac made it only for 64-bit computers. To install LW 4, you will first need to remove the
install limewire.pkg file from your Receipts folder, else OSX will not let you install an earlier version of LW.