Download the latest version of Generals Online for macOS. Unzip the archive after downloading.
Open the Terminal app from Launchpad or Spotlight Search.
Copy the following command. Make sure there is a space at the end, but do not press Enter yet:
sudo xattr -cr
Drag the unzipped Generals Online.app into the Terminal window. The path will be inserted automatically. Then press Enter.
The Terminal will ask for your Mac administrator password (the PIN/password you use to log in to your computer).
When you type your password, no characters or asterisks will appear on the screen. This is a normal macOS security feature. Just type your password blindly and press Enter.
You can now double-click the app to launch it! In the launcher, select the folder containing your original Windows game data.
~/Command and Conquer Generals Zero Hour Data/~/Command and Conquer Generals Zero Hour Data/maps/~/Command and Conquer Generals Zero Hour Data/Replays/