I've looked into this a little bit and it appears that DAZ and Poser can export files in some of the same formats that Blender can import, like Collada (*.dae) and Wavefront (*.obj), so I think all you would need to do is export from your program to one of these formats, import them into Blender, and then export them to Glest's own format (*.g3d). If that doesn't work, you might be able to use some other program as an intermediary, like how I use Google SketchUp to import AutoCAD (*.dwg) models and then export them as Collada files that Blender can use.