[captainpeter]

Allright, here's what works for me:

I'm using a Mac and VMware with WinXP Professional in a virtual machine.
Prerequisites:
-> DDSconverter (small windows app to convert the DDS files to PNG)
Those Direct3D textures seem to be in a weird format and no app on OS X can use them.

-> Blender3D (free) for the actual conversion process

1) you need the .obj and .mtl file from the screen grab
2) open the .mtl in a text editor and replace every occurrence of '.DDS' with '.PNG'
3) convert the .dds files to .png (batch process in DDSconverter)
4) copy all files (.obj, .png, .mtl) into the same folder
5) launch blender
6) file->import->Wavefront (.obj)...
7) wait - it may take a while
8) as soon as you see the scene press the 'a' key to select all
9) file->export->AC3D

I'm sure you are aware that the scaling is completely off on those 3dr files.
you need to correct that based on your view settings when grabbing the scene.

hint: have a look at line #1 of the obj file. it should contain some helpful scale factors.

you may need to flip surface normals on all objects after importing into ac3d.
you also need to set all objects to smooth shading in ac3d.

there are some additional steps which may or may not be required like mirroring the object along the x-axis.

this process will work exactly the same on Windows and Mac except that Mac users will want to move the files to their Mac after doing the DDS conversion.

cheers
peter