I purchased the IOS version for my iPhone 7 Plus but I plan to get a new iPad Air later this year. Will I need to purchase a license for that device or does my current IOS license allow me to download it on the iPad?

I'l also be getting artRage Lite later today with my XP-Pen tablet for use on the MacBook Pro. I'm looking forward to moving off of the iPhone cause it is just too small to do much with. But drawing on it beats sitting around looking at Facebook while in a waiting room somewhere.