Message you are receiving: "Camtasia 3" can't be opened because it was not downloaded from the App Store.
- Right click (Control + Click) on the Camtasia 3 in your applications folder
- Choose "Open" from the menu list
- Chose "Open" from the menu that appears
To avoid this in the future with Camtasia or other programs, you can go into your system preferences, choose Security & privacy, and under the general tab, choose the option to allow apps downloaded from: App Store and identified developers.