Family Sharing allows you and the other members of your household to share iTunes, App Store, and iBooks purchases across all your devices, without having to purchase them multiple times. While most app developers support Family Sharing, Apple gives them the option to opt out if they choose. Luckily, there's an easy way to find out if specific apps are eligible for Family Sharing. Here's how!
How to tell if iOS apps are eligible for Family Sharing
Launch the App Store app on your iPhone or iPad running iOS 8 or higher.
Search for the app you'd like to view sharing information on.
Tap on the app to view information about it.
Scroll down while in the Details tab to the Information section.
You should see an option for Family Sharing with a Yes or No answer.
How to tell if Mac apps are eligible for Family Sharing
Launch the Mac App Store on your Mac.
Search for the app you'd like to buy, or already have purchased.
Under the Information section off to the right, you should see whether or not the app is eligible for Family Sharing.
Alternately, if you'd like to view a quick list of all the apps you've already purchased on your Mac, click on the Purchased tab in the top navigation and scroll through the list of purchased apps. You should see a Not Shareable label next to any apps that don't currently support Family Sharing.
The processes above work the exact same for viewing if books in iBooks are compatible for sharing, since they're technically sold as apps. As far as music and movies, there's never been a great way to tell if purchases are shareable even as far back as iTunes in the Cloud. At least not to my knowledge. Most likely due to licensing changing frequently. This is why you see movies appear and then disappear from cloud sharing from time to time. However, if you've found a way to view whether or not movies, music, and TV items are shareable, be sure and let me know in the comments!