This issue is related to the download location of the installer, which is not marked as save from Apple. Apple removed the "Anywhere" location installation option out of the "Security and Privacy Settings" with their latest macOSs.
Please see the article below:
To overcome this issue follow the steps below:
1. Close Apple "Security and Privacy Settings" dialog
2. Open a Terminal Window under Applications-->Utilities
3. Paste "sudo spctl --master-disable" to the Terminal and enter you password
4. Start the ARES Commander Application.
5. Paste "sudo spctl --master-enable" to the Terminal (Resets the installation rights that you Mac is save again)
6. Type "Exit" and close the Terminal Window again.