The file says:
bash-2.05b$ file /usr/bin/config
/usr/bin/config: ELF 32-bit LSB MIPS-I executable, MIPS, version 1 
(SYSV), for NetBSD 3.99.7, dynamically linked (uses shared libs), not 
stripped

I think you are right. This config is an artifact from multiple 
installations on the same machine. I dont understand though why would it 
bus error.
doing ldd on it produces following:
bash-2.05b$ ldd /usr/bin/config
/usr/bin/config:
          -lc.12 => /usr/lib/libc.so.12
doing ls on the the library :
bash-2.05b$ ls -l /usr/lib/libc.so.12
lrwxr-xr-x  1 root  wheel  21 Oct 24 19:37 /usr/lib/libc.so.12 -> 
/lib/libc.so.12.114.1

and

bash-2.05b$ ls -l /lib/libc.so.12.114.1
-r--r--r--  1 root  wheel  1243760 Oct 24 19:31 /lib/libc.so.12.114.1

So all files are there. I must write the script that would cleanup all 
files that are not present in the sets so after installation of new 
version no artifacts are left. I was thinking about that for a while but 
never did it.

Regards,
Alex