No need to re download the apps but you can if necessary.
Help here > Mac App Store: Backing up your app purchases
"If you save a copy of an app to removable media (such as an external hard drive) or file share, simply drag the app back from its storage location to your Applications folder. When you open the restored app for the first time, you may be required to sign in with the Apple ID account that was used to purchase the app."
Very smart to backup your purchases !!!
I already checked the links you provided me but the first works only for iTunes and I meant AppStore, while the second does relate to AppStore, but it says to push the "Install" button to re-install, instead the only button I see is an "Installed" button that does not allow me to do anything at all.
The point is that I don't need to re-install, but I just need a back-up copy of all software already installed, because the USB key on which I stored all downloaded software has been damaged and I lost all my software stored on it.
Message was edited by: Jeremy1969
All apps I bought and installed from AppStore are free from installers: all have been downloaded and automatically installed on my HDD.
So I tried to drag & drop the apps on an external HDD but it disallows me saying that "the backup contents cannot be modified".
Then, I tried to drag & drop them on my HDD on a separate folder (which is copied & updated by Time Machine on the external HDD), but it obviously just saves a link as the app is already on the internal HDD.
Are there some settings that I should change or is there any error I make that I don't know of?