Due to some changes in Apple Mac OS X 10.8 and later it might not be possible to install the plug-in without first making some minor updates in your settings. This guide will show you exactly how to do these changes. It can look like this.
To solve this do the following:
Right-click and select 'Open'. If this does not work please select option 2.
go to: System Preferences > Security & Privacy
After that click on the lock icon at the bottom left and enter your administrator password, after that change to 'Anywhere' and click the lock icon again.
Now you should be able to install the plug-in just fine. After installation I recommend changing your settings to: Mac App Store and Identified Developers.
If after installing the plug-in in Mac OSX Mountain Lion (10.8) and the plugin closes itself along with InDesign please look into this link.