@Marty: I had donated, but I have received no email and I seem unable to login at his website... did you get an email about it?
You can contact them, I had trouble logging in with the website as it was all in Italian but you should be fine there.
I dont remember exactly how I logged in the first time as it was quite a while ago, once you are logged in you can go to contributors section and get the hd download. Track looks real good I dont think you need a 4k screen to see the advantage of the higher res textures. In general textures are fairly low res and the closer you get to objects the worse they look higher res just males them a bit sharper overall but will need a better system. It runs as good as any official tracks for me so its still well optimized.
I donated ages ago before they even had any hd versions for donators, I just appreciated the effort these guys put into this track. So cool to make a real fantasy track with so much attention to detail.