Yes You have accidentally downloaded the wrong version. That version is only for OS 9, not for OSX. Go back to that page, download LW 4.18 or whichever version best suits your OSX version. Get LimeWire for Your Platform - Lime Wire Oops looks like they changed the page, check the links at the bottom of the page under heading Past Releases. If you are a pro user, click the classic link on left side of page, choose appropriate version for your particular OSX.