Just to follow up on this, the current FreeBSD ports that are available are just for the Dropbox API, not the actual program itself. They would be useful if you wanted to write your own program that supported dropbox functionality (I think), but do not actually let you use Dropbox at the current time.
So the net/p5-WebService-Dropbox port that you installed is simply the perl interface to that API, not an actual program to run dropbox.
I hope this clears things up!
~ Ken Moore ~