TextNut OS X payment methods is changed to In App purchase since version 2.30, released at 3 February, 2016. The IAP is free for the users who already purchased older version from AppStore. For new user, the price is US$24.99. For your country or region currency price, please check out Tier 25 in App Store Pricing Matrix.

TextNut iOS is also with IAP mode, but price is only US$3.99!

Both OS X and iOS free version limits 4 internal libraries and 2 external folders. For OS X, external folder is folder in your MAC. For iOS, it means dropbox folder.