Some users on Mac OS X have reported that the bonus content installer for KeyShot is shows as being damaged.
There's actually nothing wrong with the file -- except that certain OS X security settings don't like it.
Simply change your OS X security settings (part of Gate Keeper) to "Allow downloads from anywhere." This will allow you to open the file without even needing to download it again.
If you didn't save the file after downloading it and your link has expired, please submit a Support ticket to have your link reset.