Ok, here's all you need to produce this grass.
Download the file (see below), unzip the folder, and put the mlib and plib in your renderer's libraries folder, along with the bmp. You may need to open the plant editor and re-direct the various settings, I'm not sure if you'll need to or not. If you do, for each leaf in the plant definition (there are four) go to edit>geometry and check that the location of the opacity map is directed correctly, then go to the “settings” tab in there and make sure the material definition is pointing to the correct materials.
To use this in a rendering, make a plane and assign the “grass leaf - heath3” material to it, then insert the grass as a plant, making the area of the groundcover the same size as the plane you just made.
Hopefully that will do it… sorry it's such a pain, but it seems like that's about the smoothest way to get a complex plant transfered with the current methods available…
If anyone gets a rendering with nice results using this grass, I'd love to see it…
http://en.wiki.mcneel.com/content/upload/files/Heaths_grass.zip