The program can not be opened because it comes from an unknown developer.
What does that mean? By default, Apple developers have chosen that applications that are being used on OS X must originate from the App Store or from an authorised developer.It's a security measure and you should be really happy about it.However, if you are using a program that does not come from the App Store or an approved developer, you must change the settings.See how to do it right here.
Click on the Apple icon and open the System Preferences...
Then you click on "Security & Privacy"
Click on "Open Anyway"
Now you can close the System Preferences and open the program.