Doctor XFizzle

I doubt it's for "free" eventually you will end up paying for something

"We have two currencies you can earn in the game based on different drop rates. If you can’t wait for the timed rewards, you can access in-app purchases to acquire more. When you play the mini games, you can also choose several items with values that will impact the final XP gain of your pony to earn more currency."

But you don't have to buy anything.