GrammarFlip is iPad compatible. GrammarFlip was built with a responsive design which means it should work on a tablet, laptop, or computer. Smart phones have slightly different settings, so based on the device, some resolution settings, layouts, and functionality may not be supported.
There is not an official GrammarFlip app right now, but a simple "add to home screen" step on your iPad will allow you to access GrammarFlip with a single click, similar to how you would access an app downloaded from the app store. Here is a simple YouTube video on how to do just that: https://youtu.be/Mvee2Ct8BTg