If you are using Stuffit 8 (Deluxe, Standard, or Expander), this application will not run after you unstuff it. The ".sit" format does not know anything about Unix permissions. Stuffit versions 7 and earlier automatically give run permissions when unstuffing, but beginning with Stuffit 8, permissions are set to deny execution. The developer must switch to the ".sitx" format in order to preserve permissions and allow users to run the application.