This is likely because the app is not signed correctly, but until this is fixed we can work around it. Open the Terminal (it’s in the utilities folder in applications) paste this in “xattr -cr “ (without the quotes), then find the learn GDScript app in finder, copy it and paste it after the previous command. Now it should look something like this:
xattr -cr /Users/user/Downloads/Learn\ To\ Code\ With\ Godot.app
Press enter, and now it should open.
To clarify a bit, this basically tells your Mac to ignore that this app is not from a verified developer.