David told me that he made a mirror image of the hard drive from his old iMac, to use on his new iMac. In my opinion, that can lead to a multitude of problems with incorrect device drivers. And NSD Pro 6 works fine for all our other customers with Gatekeeper enabled (after Control-Clicking it to Open it the first time NSD is run).
To be clear I didn't mirror or image one machine to another, I used the Mac OS built in migration assistant to copy all of my documents and apps from one system m to another. It has always worked very well for me and I suspect it's designed to make sure that old system field and drivers are updated with the migration. It's only purpose is to prevent you from having to re install all of your 3rd party software.
In my opinion (as a non expert) this issue was not related to the migration of one iMac to the other. It's specifically a Mavericks OS issue. I'm basing this on the fact that when I went back to my old iMac (which had been updated to Mavericks prior to the migration) and attempted to install NSD 6 there I got the same crash symptoms as I did on the migrated iMac. There's always an amount of variability in how each machine is set up and perhaps something on my system interacted with Mavericks and Gatekeeper to create this issue, but the problem was certainly there in both OS's independent of the migration. I have no doubt that others running Mavericks are having no issues, but it was obviously the critical factor in my case.