Hi Hywel,
There are two possibilities for getting the request for the serial key as shown in the picture:
1. Installing a SuperPack, such as the one for Busier 2 when you don’t have New Horizons installed. A bug in the SuperPack installer allows a pack for an improved ship to be installed even though the basic ship is not installed.
However, there has not yet been a pack for Atlas, so this explanation does not work for you. So that leaves #2:
2. Copying a ship folder from someone's New Horizons into the objects folder of a game without New Horizons. That will not be successful because it will generate a request for the serial key.
That is a violation of the EULA and cause for disciplinary action.
Regards,
Marty