A post on Reddit has a lengthy response from Ironmace, the developer of Dark and Darker, following the recent DMCA takedown of the RPG amid allegations it includes assets stolen from Nexon. This goes on and on for anyone with an interest in a lot of details and a lot of time to dig through them. With apologies for any spoilers, we'll jump to the conclusion to try and sum this up:

Given the information presented, it is difficult to believe that Nexon, in good faith, could reasonably believe that Ironmace has infringed on the copyrights for their P3 project. They also provide no actual evidence that Ironmace misappropriated Nexon’s trade secret information in the creation of Dark and Darker, but instead base it on circumstantial claims. Finally, they accuse Ironmace of a flagrant breach of Valve’s SSA and SOCR, restricting our ability to provide our game to players on the largest mainstream PC game platform and severely obstructing our ability to do business. Ironmace requests that Nexon renounce their baseless claims. If they would like to compete on merit, we welcome Nexon to promptly accommodate the comparison of source code, custom assets, and design documents with the police to quickly and decisively put an end to this matter.