Lights settings, camara positions and so on are general concepts for 3D programs. A three-point lighting in Poser and Cinema 4D will give you comparable results.
With the ProPack I can import 3D modells from Poser into Cinema 4D but not the lights or camera position. Now if I write a Cinema 4D plugin wo import those too (which is dirt easy, would cost me less than 3 hours) do I need written permission from CL? If CL doesn't enforcing the copyright at this point where do they draw the line?

If Poser doesn't play nice with other application it will never lose its toy-status. Using different applications for differtent tasks is an integral part of a professional workflow. Proprietary file formats are anathema to serious users.