Since the release of Mac OS X Mountain Lion, it is possible that the message: ?Unable to open [nom de l?application], because this app comes from an unidentified developer?Appears when you try to open an .DMG file, for example.
This means that your security preferences prevent the installation of software downloaded from the internet. To get past this annoying message, go from your Mac to System Preferences> Security and Privacy.
In the General tab (open by default), click on the closed padlock at the bottom right of the window. Enter your password, then click Unlock. Then click on the ?Anywhere? radio button and then on ?Allow from anywhere? when the warning window below appears:
Close this window to launch your application again. Enjoy! ? Of course, you should always be wary of applications downloaded from the internet, and we recommend that you check the source of the software before installing it.