When you are trying to launch a program downloaded from Internet on Mac OS X and receiving the error message that can’t be opened because it is from an unidentified developer then you can trying the following.
Step 1: Click Apple icon and select System Preferences from the menu list.
Step 2: In the System Preferences screen, click the Security & Privacy option under Personal section.
Step 3: This should display the following Security & Privacy screen. Click the lock icon and enter your password to make changes to the Security & Privacy settings.
Step 4: Then navigate to Allow applications downloaded from section and select Anywhere option. This would display prompt asking your confirmation as this option would make your Mac less secure. Click Allow From Anywhere option to confirm the changes.
Now you should be able to run any downloaded application from untrusted publishers.