By default, Macs with (starting with OSX Mountain Lion) have a firewall setting that blocks all third-party developer's apps.
You may see an error message such as "Revizzit" is damaged and can't be opened...
This is not actually true, and Revizzit and other third-party apps are unfairly being labeled as a "problem" as pressure to start paying Apple to "approve" us.
To correct this, you will need to follow these steps to change your installation permissions:
1. You will need to allow the application to install from your system preferences. Start by opening your “System Preferences”. Click on “Security & Privacy”.
2. Click the lock icon to make changes to this panel.
3. Click the “Anywhere” option. Note, once you have installed Revizzit, you can change this preference back.
4. Again, choose the “Allow From Anywhere” option.
5. Once you've done this, Revizzit can install normally.