It's a small utility Application for launching MixEmergency. From the ReadMe file: "MixLaunch is a small utility application that can be used to launch the MixEmergency, and keep it launched. For example, if MixEmergency is closed while MixLaunch is running, then MixLaunch will relaunch MixEmergency. To set the path to your MixEmergency application, simply drag and drop the MixEmergency application from the Finder into MixLaunch. It is recommended that you run MixLaunch during your set if you intend to load media that you have not tested beforehand, or have not encoded yourself, so that MixEmergency is automatically relaunched if a bad file causes a crash." It's more of a safety-net type thing - to save you from having to panic to find and re-launch MixEmergency mid-set if a bad file were to ever crash it.
