This guide has been largely replaced by https://help.yoyogames.com/hc/en-us/articles/216753558
We have been made aware of an issue with the latest Mac OS concerning security permissions. This error makes you believe there is something wrong with GameMaker for Mac. You will see this message for non App Store downloaded applications.
The error message shown.
This message can be fixed by changing your permissions by clicking the Apple icon and then "System Preferences".
Within System Preferences click on "Security & Privacy".
Go to the General Tab and click the padlock in the lower left.
You will need to enter your Name, Password and click the unlock button.
After this is done this will unlock the feature that we wish to use. Select the "Anywhere" checkbox. After this you will see the dialogue below and you can select the "Allow From Anywhere" button.
If the "Anywhere" option is not shown, you may need to enter the following on the Terminal:
sudo spctl --master-disable
Now you should be sorted and you can now open GameMaker for Mac.
If you had used the sudo command mentioned above then please ensure you re-enable this setting as it's for your security. You can do this by entering the following on the Terminal:
sudo spctl --master-enable