Has anyone ported the GNU dld package to NetBSD or is there any other
      way of getting dynamic linking/unlinking of object code at runtime
      in NetBSD?
   
   they exist, but aren't documented in any man pages (i think).
   if you have access to sunos, or a svr4 machine, `man dlopen'
   should give you the info you need.  perl5's dynaloader uses
   them (look in perl5.xxx/ext/DyanLoader/dl_dlopen.xs).

i forgot to lists the differences (thanks adam):

netbsd doesn't current have dlerror().
netbsd's dlsym() *requires* leading underscores.
netbsd uses <link.h> not <dlfcn.h>.