The official source for NCS Dummy is the NCS Dummy thread on Bimmerforums.

Users can now run the software from a portable drive. By adding a NcsDummy.ini file to the application folder, all settings are saved locally instead of in the Windows Registry.

Before installing NCS Dummy 6.10, ensure your environment is ready:

Includes a reverse lookup where clicking an address in the hex viewer automatically highlights the matching function in the graphical editor. System Requirements & Setup

Compare two different trace files to see what has changed or explore what features a module could support before even connecting to the car.

NCS Dummy is strictly freeware . If you find a site charging for it, it is not an official source.