Under rare circumstances, OS X may claim that "Fade In is damaged and cannot be opened. You should move it to the Trash." when you are trying to run it after installing (i.e., after dragging it from the mounted installation .dmg to your Applications folder).
This may be due to a bug or glitch that some users have encountered with OS X's Gatekeeper security functionality.
There are a couple of things that can be tried if this is the case, if you're comfortable:
1. In System Preferences > Security & Privacy > General, temporarily change Gatekeeper settings to “Anywhere”. Then try to open Fade In. Then immediately change Gatekeeper settings back to what they were.
2. If you’re comfortable using a command line, then from Terminal:
xattr -d -r com.apple.quarantine "Fade In.app"
Either of these should remove any "quarantine" attribute that has been mistakenly assigned to the Fade In application package an dallow it to be run.