Mac os x mountain lion is no doubt one of the best os designed to full fill the users as it designed considering the modern day computing needs, but this time again mac os has become more limited in a way what you can install and what you cannot. As most of the mac os apps are now available through mac app store but there are few good developers who make their apps and they are not on app store.
In such cases you might download an app as .dmg which on extracting might open folder which have .mpkg file and in case you want to extract and install the app just like you do on older macs, it will through a error saying the following error message as shown in the snapshot below.
Now in order to get rid of this error you just need need to right click on the *.mpkg file and select Show Package Contents and locate the .pkg file and then press control key and then click to launch it and then you will see the open button to forcefully run or install it.
Another way to solve this is to right click on the app file and select open to run it or install it without any warning, but we recommend that you should do it for the apps you have downloaded from authoritative sources.
If you completely want to get rid of this error and you would like to install many apps which are not on mac app store but you would rather download them and install separately, in such cases you should change the privacy security settings under system preferences in mac os itself so, that it does not show you the warning when you install an app.
This is how you solve the problem of installing unindentifeid and other apps which you download and install from sources other than mac app store.