After downloading KIELER, Mac OS quarantines the application and, for some reason, considers the app broken and wants you to move it into the Trash.
Hence, if you want to use KIELER on your Mac, you have to remove the quarantine flag manually. You can use the following command:
xattr -rc com.apple.quarantine ./Kieler.app
xattr -rd com.apple.quarantine ./Kieler.app
depending on the Mac OS version