Starting with Mac OS X Mountain Lion the Gatekeeper was introduced that by default does not allow users to run applications downloaded outside of the App Store. In this situation are also the RationalPlan users that are downloading our products directly from our website.
Now since Mavericks is a free upgrade from Mountain Lion the same restriction applies. Hence if you find yourself a fresh Mavericks user and when trying to install RationalPlan you get an error like this one:
you can solve it by going to Apple menu > System Preferences… > Security & Privacy > General tab and under the header “Allow applications downloaded from:” check the Anywhere box. This will allow you to install RationalPlan. However after the install is complete you might want to set it back to Mac App Store and identified developers.