I don't know whether this should be added in case anyone wants to play the version 1.2 of the disc version unmodded. I found this while poking around in the DX2Main.exe file since I couldn't get 1.2 to work on Windows 10.
DX2Main.exe will not start on its own and tells you to run DX2.exe. I assume DX2.exe is the protected executable. However, if you start DX2Main.exe with the command line switch "-NoIMeanItReally", it launches and seems to run just fine, bypassing the disc check and (now possibly non-functional) copy protection.
I should probably note that when I tested it, it worked properly from a shortcut or the run option, but would crash when launched from a command prompt. That might be something specific to my system however.