"Word Chums" is free to download as of 2015. There is also a "Word Chums Pro" for $3.99. A free version is available on both Android and iOS devices and through the Amazon.com app store.
The "Word Chums" app does offer in-app purchases. These offer an amount of coins in return for a sum of real money. These prices range from about $0.99 for 500 coin to $49.99 for 40,000 coins (roughly 800 coins for a dollar). The Pro version is available on iOS and offers an experience that is ad-free. It also comes with a 1,000-coin bonus. "Word Chums" is rated E for Everyone and was developed by PeopleFun, who are also the makers of "Adventure Smash."