Hey guys,
The shortest way to describe it is - CIG is responsible for game and art direction, while D13 is responsible for the production and implementation. But it ain't that simple.
Art Direction for example was primarily designed and led by CIG's Damian Zielinski, but it doesn't mean that the whole art team at D13 led by Timm Schwank didn't add creatively to the project.
Gameplay was primarily sketched and supervised by myself (Tomek Gop here), but the whole gameplay team at D13 led by Sven Hammer greatly reinforced the creative manpower during implementation.
As for the story and such, we also shared responsibilities. Jan Klose, the Creative Director at D13 managed the topic but CIG team (including me and our Producer, Blazej Zywiczynski) worked hard to support, both creatively and execution-wise.
Of course we can't forget that the majority of game assets was created on outsource, so yeah it wasn't a very simple structure but all in all it was a co-development, as both parts actively designed and produced the game.
Let me know if that explained things folks.
Cheers and a happy 2015!