Ah, I'd forgotten that too--I had done
kldload linux
(necessary to install the c6 ports), but hadn't mounted
linuxprocfs(5). The port had built, but when I started it, I was unable to get past the accept screen. (When pointing people to the instructions, if mention of loading and mounting linuxprocfs isn't in them, it might be useful to add it.)
I still can't get sound or camera working with it, but haven't yet spent much time trying. (Sound and camera do work on the machine.)
Just for fun, I also tried to install it on a 10 beta, but it didn't succeed, saying that
bsd.linux-apps.mk test failed, suggesting I remove the IGNORE line in the make file for openssl-compat.
As the
bsd.linux-apps.mk is one of the files provided for the skype4 port, and looking it, with my limited knowledge, it wasn't obvious to me which of the IGNORE lines needed to be commented out, and did that also mean I should comment out the if statements in which they were, I stopped at that point.