Apple provides a number of layouts for various purposes in OS X--mainly for international layout differences, but also for variations such as Dvorak. Besides localization purposes, there are also times when specialized layouts may be useful for certain technical applications, to just disable a key, or to swap two modifier keys' functions on a standard keyboard layout. Regardless of the reason, people have wanted to easily edit or create new keyboard layouts in OS X, but have not been able to do so with any utilities Apple provides.
