Xamarin (Windows) and MVVMCross

I was experimenting with Xamarin and MVVMCross. When I run or build the application I get the following error:

C:\Program Files (x86)\MSBuild\Xamarin\Android\Xamarin.Android.Common.targets(5,5): Error XA9003: Assembly System.ServiceModel, Version=2.0.5.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35 requires Business (or higher) License. (XA9003) (MvxTest.Droid)

Why am I getting this?