I just finished downloading and installing Visual Studio 2015 Enterprise with Update 2 via my MSDN
subscription. I saw the news from Build indicating that
I use Visual Studio 2015 Update 2, but in Tool => Option => Xamarin => Other i choose Alpha and Visual Studio installed Alpha version. Now i choose Stable => Visual studio auto install Xamarin Stable version => Work like charm! :)
You definitely shouldn't be getting licensing errors with the newest tooling. If you already had Xamarin installed in Visual Studio before updating to Visual Studio 2015 Update 2, you may be on an older version of Xamarin for Visual Studio.
Only the latest version of Xamarin for Visual Studio will allow you to work in Visual Studio without a traditional Xamarin license. Can you ensure that you have version 4.0.3.214 installed? You should be able to find that information via "Help -> About Microsoft Visual Studio -> Copy Info [button]"
Any version older than that will need to be updated. You can follow the instructions for Visual Studio here to check your updater channel and force a check for updates.
Version 4.0.3.214 is currently in both Beta and Stable channels.
Also ensure that you have installed the latest Xamarin bits on the Mac build host that you are using. The error may come from there instead of Visual Studio.