As noted by MSDynamicsWorld.com, Microsoft published to its download center software licensing terms of use for Dynamics NAV 2015 for Android tablets, iPads and Windows 8.x, and then it quietly made available in the iTunes, Google Play and Windows Stores versions of the Dynamics NAV ERP apps.
The new Dynamics NAV client apps are free, but require Microsoft’s Dynamics NAV ERP on the back end. Client supports different sets of features depending on which version of the Dynamics NAV server apps they use.
Source: MSDynamicsWorld.com