I have Wolfgang Langhoff's book 'Die Moorsoldaten', where he writes about his memories of the camp and the writing of the song. I'm not sure it is still in print, but I could try and copy the relevant passages some time.
Langhoff - and Esser too, I believe - were left-wing actors. Langhoff rose to lead the East German state theatre although I believe his relationship with the powers that be was always somewhat uneasy. His son, Thomas Langhoff, is a theatre director as well.
I'm not sure about Rudi Goguel. I think his melody was added later, and that a different one was used originally, but I'll have to look this up.
Boergermoor was no extermination camp in the later sense of the word, but it still wasn't a Sunday school. In one neighbouring camp, Esterwegen, Peace Nobel Prizewinner Carl von Ossietzky was tortured and his health undermined so he died shortly after being released. Others weren't, and died there. - Susanne