Witgui is based on the wit and wwt executables which are part of the Wiimms ISO Tools. These tools are the core for listing and converting your games and most of the other features that Witgui offers.
wit and wwt can be downloaded from the File menu with a single click. After a successful download, the executables will be placed in the Application Support directory.
If you already have your own installation of wit or wwt, you can locate them by selecting “File > Locate wit/wwt …” while pressing the alt/option key. By default Witgui tries to locate wit and wwt in the following order: it first checks the supplied installation (if any), then searches in the Application Support directory and last in “/usr/local/bin”. When selecting “File > Download wit/wwt”, any reference to the custom installation path will be removed.