As I mentioned above, that it was included with Deskscapes1 and you are now on Deskscapes3 which has a few newer dreams like the Vintage dream [indeed a new variety- hybrid]
So, the only possible way to get it is to install the older version of deskscapes on a machine and copy the GrassyField .Dream file located mostly at C:\Users\Documents\Stardock\Dreams
It would also be a good idea to do it on a friend's machine who does'nt know about Deskscapes yet, even he/she would be glad running a beautiful animated wallpaper on their desktop !!