As I understand it, no code was lifted "wholesale" from CP/M to QDOS.
However, the basic principles (not a secret) and interface (evidently, this being a clone) indeed were. Code underneath was hacked anew, and if the mystery was too great, a debugger would be used to inspect what CP/M was actually doing in there. It's a honest-to-God reverse engineering effort by Tim Paterson that every backstreet China dev shooppe would recognize. And maybe a few Open Source projects, too.
There is no need to polarize.