Thats great, thank you very, very much for your help. I read the documents you talked about, then downloaded the pkgsrc tree, installed the build-essential package from OI and tried to run the bootstrap script.
At first this failed, and the reason was the /usr/gnu/bin in $PATH. There is obviously a mistake in the netbsd description, cause as I removed /usr/gnu/bin from my path, the bootstrap script went fine.
Then I compiled the ctwm from pkgsrc, what costs a little bit time. However the run was successful and now I have a better wm running.
So the largest problem of OI is solved: The lack of applications. I now have the wide world of NetBSD in front of my eyes. Fantastic!
This ist the pure ctwm, only with the system.ctwmrc:
