Apple has been under a lot of fire recently from the European Union commission for labeling apps with in-app purchases as 'free'. Also, there have been countless scandals related to unauthorized purchases made by kids. Apple has tried to fix this in iOS 8 - the “Ask to Buy” feature notifies parents before a child can make an app or in-app purchase.
Also, Apple has recently also created a Kids Section on the App Store with even stronger protections to cover apps designed for children younger than 13. And now the company is taking the next step - it has relabeled all free apps on its iTunes and Mac app stores with 'GET'.
This is a little vague, as it sounds more like a call to action, than a price, but it makes it clear that while you can 'get an app', this doesn't mean it is entirely free.
At the moment, 11 of the top 20 “free” apps in the iTunes App Store use the “freemium” business mode, which seems to be the most successful one, as it represents 92 percent of all revenue on iOS and 98 percent of revenue on Google Play in 2013.