If you get the below message with IOS9, Here is the tutorial on how to resolve this issue.

Step #1. Open the Settings app → Tap on General.



Step #2. Scroll down a bit, and tap on Profiles.



Step #3. In the list of “ENTERPRISE APP”, tap on the app you wish to trust.



Step #4. Now tap on "Trust (name of Enterprise App)."



Step #5. You will be prompted with a pop-up to confirm the operation, tap on Trust.

That's it, exit from Settings app and tap on the app you wish to run, you will no longer be getting any warning message, and the app will run successfully.