Great question — answering as the UphillTech team:
VirtualBox shared folders are still not suppported on FreeBSD. A FreeBSD ports committer has confirmed this on the FreeBSD mailing lists as of (2014-06-24): Shared Folders for FreeBSD guests are not supported yet [...] There is some draft code and a kernel module for it but it's not working yet. If you want to follow the state of the port, please search the mailing lists. There is also the #freebsd-vbox IRC channel on Freenode. It was posted to the freebsd-hackers mailing list at the bottom of this post . You will find developers there. Finally, here is what the virtualbox-ose-additions port currently supports according to Chapter 22.2 of the FreeBSD Handbook as of today: The VirtualBox™...
Full answer by Francis Harbison: https://unix.stackexchange.com/a/155373 (CC BY-SA 4.0).
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