Its clear there is little interest in this DK compared to the nRF52 version. I got instructions for that platform that actually worked.
Not so for the nRF51 DK. But I am stuck using it, otherwise I would toss it in the trash.
Follow the procedures to install SoftDevice from Keil. It actually worked. What the instructions did not tell me was that the memory addresses were wrong. When I tried to install the demo application (health thermometer), I got the dreaded Cortex-M0 error.
The reasons were one of several according to this site one being no power to the chip (obviously not the case since SoftDevice loaded). The other reason was an address conflict. Sure enough, the address for the SoftDevice installation in Keil was the same as the application space. Arrg. So now I had to erase that and try a re-install. Was able to erase but not re-install. At least with Keil. The docs said I had to use nRFGo Studio. Arrg! More crap to install. Installed but did not work. Uninstalled. Out of desperation I used the Nrf Connect tool and that did work! But now when I try and install the hts example application I get that dreaded Cortex-M0 error with the unable to read memory location 0x20000000 which is the start address configured in the flash.
I still have not figured out a solution and there are so many conflicting and incomplete instructions that I don't know what to do.
Would be nice if there was somewhere a SINGLE clear, correct, and tested set of instructions to use the nRF51 DK with the examples in the corresponding SDK.