I missed it? (head shaking) Sorting through the comments I feel like I missed a great idea, Plagiarism is actually easy to detect with some type of software, anybody have a copy of the original idea I missed? looks interesting.
As far as I can tell the OP is the original idea but I don't think Invictus are going to develop this as they are working on other projects such as Keyhotee. Therefore I, and do correct me if I'm wrong, believe this idea is free to be developed.
I too figured there is already existing software that can detect plagiarism however software I am aware of (TurnItIn) will pick up things with quotes in them for instance and flag those as plagiarised. This software generally relies on a human source to then manually go through those articles which have been flagged to confirm if they are plagiarised or not.
My thinking was a similar system can be implemented for the DAC with there being people who check flagged content to see if it is a copy or not. This check could be sent to multiple people to prevent bots from just saying they are or aren't plagiarised with an individual being given a score which is based on the number of correctly identified documents.
Ultimately, this system would be useable with not only text files but music, video, games etc etc. which leads me to think it would be best to create Media DAC for this purpose, which can be used by other DAC's focused on specific media (say a sports magazine DAC or a medical journal DAC etc.).