OS X features a security feature called Gatekeeper which prevents the installation of malware by controlling the types of software that can be installed. While Kodable is signed with the proper security certificates, Apple introduced a bug with a recent version of OS X that prevents apps created with the newer versions of OS X to work with computers running versions of OS X older than El Capitan.
Fortunately there are two ways to fix this.
1. Update to the latest version of OS X (Recommended)
This problem should be fixed for all users running OS X El Capitan version 10.11.5. El Capitan is a free update that offers many security improvements as well as new features.
2. Temporarily Disable Gatekeeper
If you cannot update OS X, you can still install Kodable by temporarily disabling Gatekeeper during installation.
1. Navigate to System Preferences from the Apple Menu or from the Dock.
2. Click on the Security & Privacy preference pane, under the Personal header.
3. In the Security & Privacy pane, click on the Lock icon on the bottom-left.
4. Enter your Mac's username and password and click Unlock.
5. Click the radio button next to Anywhere.
6. When prompted, click Allow From Anywhere. You can now install any compatible application on your Mac without the installation being blocked.
After updating any necessary software, follow the above instructions until step 5, and click the radio button next to Mac App Store and identified developers. Then close the System Preferences window.
Note: Gatekeeper only needs to be disabled during the initial installation and running of the application; after that, it can and should be re-enabled.