It would be slightly true about the copyright infringement as they are no longer made, therefore it becomes a cloudy issue. Same goes for pattern replica parts for obsolete parts the world over. I've never been into direct copying and to be honest I wouldn't be setting up a business on the back of someone else's time and effort which in the case of the DP rear sets would in my estimation take about 2 hours for a reasonably proficient CAD person to model on screen. My only need for loaning parts is to gather dimensions etc and basic layouts and what bike(s) they fit on. As I've already said I can't go buying bits left right and centre as it would cost me a fortune and I would be far worse off than simply asking to loan them. Giving someone a set of whatever I make is worth its weight in gold and far cheaper overall and both parties stay happy and once I have important/critical dimensions etc it would be a simple matter of moving some elements about on screen to make style/design/size changes and then resetting the CNC program (re-posting) as the CADCAM software I use is totally parametric and stretches everything about keeping important elements still as I do it. This is a very simplistic explanation and is slightly more in depth than I've written.
Blatant copying and trying to pass off as an original or purporting to be DP part is asking for trouble and would have trading standards knocking at anyone's door should the original designer/copyright holder make a complaint.
Hi final_edition, I've edited my reply. Poor research and not checking the details by me I'm afraid. Hands up to a mistake.