The main problem is that you normally can't use the meshes in another application (see EULA).

DAZ has started licensing some meshes for use in games etc., see -> http://developer.daz3d.com/

Once you get past that, you'll need to understand that you'll effectively have to replicate Poser's rigging calculations to get the models to work in the way you expect (not forgetting that hands & fingers are particually tricky).

Rather than starting completely from scratch, you should look into the possibility of using the MakeHuman meshes and/or Blender's game engine.