The openbox port installs the required header file in a
location that the obconf port doesn't expect. To fix this,
patch the obconf code as given in this patch.
Fix: Apply patch below.
Over to maintainer
I made the openbox port install its headers in a different place,
so they should be found during compilation of obconf. Please let
me know whether this works for you.
Submitter reports that the ports are working correctly now.