Problem: Doom 3 MAC APP STORE version fails to launch.
Deactivate your internet connection and launch the game. After the initial launch is successful, you can enable your internet connection.
Problem: Doom 3 Digital River version (.dmg) fails to launch.
Workaround for issue:
The following steps must be run on an account with administrator access and not a standard or guess account. A password is required on the account.
1. Launch Terminal from /Applications/Utilities.
2. Copy and paste the following command into terminal: sudo xattr -d -r com.apple.quarantine
3. After com.apple.quarantine, add a space.
4. In Finder, locate the Doom 3 application (this is normally in /Applications).
5. Click and drag the application into the Terminal window.
6. Select the Terminal window.
7. Press enter.
8. When prompted, enter the user account password (You will not see the password in the Terminal window).
9. After Terminal displays a new command line, exit Terminal.
10. Doom 3 should now run without issue.
Notes: This command only needs to be entered once. Subsequent launches should work without issue.