I just downloaded, the current combo 0.3 for OS X. I could start it from the dmg however, was unable to launch it from my case sensitive filesystem after copying it.
OS X said: "you can't open the application ... because it may be damaged or incomplete"
I found that the Info.plist contained: CFBundleExecutable (“Executable file”): wxMupen64plus
However the executable file was named "wxmupen64plus" (no capital M) which results in no application launch because the system can't find the executable.
I fixed it by changing the case in the Info.plist. Alternatively I could have changed the filename of the executable.