All right.

The first problem with the Bushwacker is that the figure has been scaled up 500%. This is why you're seeing only part of it in the WD's preview window. I don't know if the scale has any other effect on Walk Designer, and don't feel inclined to experiment.

The second problem is that the Bushwacker uses a nonstandard naming convention for the legs and feet. If the WD doesn't find certain properly-named body parts (hip, lThigh, rThigh, lShin, rShin, lFoot, rFoot), it won't apply the animation to the figure, let alone make it follow the path, even though it seems to be moving in the WD preview window.

I learned that second part the hard way when adapting Bill Redfern's legless robotic creation, F.L.O., to Poser. I had to give the figure legs (properly-named, of course) before it would work in Walk Designer and follow a path. I hid the legs so they wouldn't be visible, of course, but they still had to be there.

The third problem is that the animated poses included in Walk Designer are designed for figures with standard leg names. So the Bushwacker's legs wouldn't animate with those poses, regardless. Try applying one of the poses directly from the Library, and you'll see what I mean.