QTPlayerFullscreen is obsolete, because non-Pro Quicktime Player can play movies fullscreen since 7.2.
In non-Pro QuickTime Player menu, View > Fullscreen feature is disabled. But the player can play fullscreen via the AppleScript. So QTPlayerFullscreen is run the script from View > Fullscreen menu. I think it's just a shortcut, not crack :-)
To install, please copy QTPlayerFullscreen/ folder to ~/Library/InputManagers/ and relaunch QuickTime Player.