Richard,
I don't think that we will ever be able to run a FW legacy app on Windows RT (unless you use VNC, or similar)
What I have been able to do so far, is to build a WinRT app that uses Harbour as a library, and used a little part of its GUI. More a proof of concept than a ready to be used product. Also, I stopped its development for some time, as I want to go further and try to deliver a Harbour based solution for all mobile devices (WinRT, iOS and Android). And I am delayed cause FWH requires a lot of my time and work
If you are in a hurry and need to deliver an app for it, you should use Visual Studio and code your app from it using Microsoft tools.