To keep the near objects in focus, you want to set the FarDOF to make things in the background blurry, so:
fw.GetRenderer().SetFarDOF(true);
fw.GetRenderer().SetFarDOFRange(Vec2(5,8));
fw.GetRenderer().SetFarDOFStrength(1.0);
This will make anything past the starting point of 5 meters from the camera blurry... its hard to tell if the ending range makes much differences other than it obviously needs to be a higher number than the starting range. I assume it does a gradient of blurring between the two ranges. The strength is what is crucial and sets the amount of blur, where it appears 1.0 is the highest value and 0.0 is the lowest.
***Edit-- wmaass, are you using bmax? If so the commands you need are:
fw.Renderer.SetFarDOF(1)
fw.Renderer.SetFarDOFRange(Vec2(5,8))
fw.Renderer.SetFarDOFStrength(1.0)