From the GNU Dbox2 homepage (http://www.tuxbox.org/index.en.html), in the documentation section it refers to NFS. As far as I'm aware NFS is and always has been "Network File System" which is the prevalent way of setting up file shares on a Unix/Linux-based system.
The LMGTFY link I provided details how to install the NFS daemon on the DNS-323 which gives it the ability to set up said shares which Dbox2 needs access to write over the network to another *nix system.
Below is a section from the Dbox2 Docs:
NFS
You need an nfsd. The directory for NFS has to be exported. This is done in /etc/exports
/dbox2 dbox(rw,no_root_squash)
activate this by exportfs -a
or do a /etc/init.d/nfsd restart
You would need to do something similar from the 323 once the NFS daemon is installed. I'm not saying it's going to be easy. It's entirely possible to make this work.