Here is a very odd solution that worked for me. I found it by pure luck.
1)Download the software from X-Aviation to your desktop.
2)Extract it with the native Apple un-zip tool. A new folder with the name Maxx FX 1.0 will be created.
3)Drag the “setup-osx” file out of the Maxx FX 1.0 folder to the desktop.
4)Double click the “setup-osx” file and get the “corrupt or incomplete” file error.
5)Close the error message box, and drag the “setup-osx” file back in to the Maxx FX 1.0 folder.
6)Double click the “setup-osx” again, and the installer will launch.
I have absolutely no clue why this works and the logic behind it, but the fact is that it does.