We allow all users backup of network disks / NASs per Jottacloud account. We do not offer own clients to network drives, so the backup of such equipment must go through a computer running Jottacloud client. One can only use Backup to upload data from network drives, you can not use the sync folder.
To backup a network drive, simply add folders from the NAS drive in the same way as you would add folders from an external disk to "Backup".
The disadvantage is then that all datatraffic will go through the main machine, but it's also a little easier to keep track trough the Jottacloud client available from your computer.