it's a missleading error by Apple

by gubatron - 12/23/12 6:40 AM

In Reply to: FROSTWIRE for MacBook Pro by VOLTA1960

The installer is not damaged and you dont need to trash it.
After MacOs 10.8 Apple made it a default setting to not allow the installation of Apps that dont come from their app store. Luckily thias is still a setting you can change.

Go to System settings > Security preferences and allow third party apps to be installed.

Here are instructions with pictures