I know Nem has also created a program to create displacement maps. While this program does not have all the fancy bells and whisles, it does have a few advantages.
1) All processing is done using 16 bit greyscale images. 8-bit images (including 24/32 bit fullcolor images,are converted to 16 bit greyscale images before creating the terrain. All scaling and smoothing is done using 16 bit greyscale. This eliminate the stairsteps in generated terrain caused by having only 256 levels of grey.
2) I use a bicubic interpolation scaling algorithm. This generates a better image if the size of terrain is significantly different from the size of the texture image.
3) dispgen includes an algorithm (pat. pending) for fixing texture stretching on the vertical parts of the terrain
