This isn't as bad as some forums, but in general, if you come on here criticizing FreeBSD there will be those who jump on that. Tribalism is alive and well, look at US politics. (Or other countries, but I live in the US, so that's the one I know best).
Quick answer--try using the CLI for hplip rather than the GUI, it often, in my experience, works better.
Long answer.
Even with Linux, which, at least in many distributions makes the desktop easier to do than FreeBSD, I would see people having trouble with the hplip GUI tool, but succeeding if they used the command line one. That might have only been with Fedora, and I want to say that I think they had a broken hplip, even the CLI version, and you were better off building it from source, but I may be misremembering. Anyway, you could file a bug, pointing out that it's working on GhostBSD, but they will ask you for further information, and you have to decide for yourself if you want to spend the time.
If you want to use FreeBSD as your desktop, you will often have to do more work than you would with Linux. If your job is FreeBSD based, or you're eager to learn it, and want to use it as much as possible, you can certainly do it, but there will be the odd annoyances, such as the one you're having now.
Personally, I use CUPS for printing, though I did use the lpr method just to see if I could do it.
wblock@ has a nice page on getting it to work at
http://www.wonkity.com/~wblock/docs/html/lpdprinting.html. CUPS might Just Work(TM) for you, but if you definitely want to use hplip, then I go back to my quick answer, try the CLI version and see if it works. Afterwards, the usual suspects, printer pingable, etc.