I assure you that if NAS is turned on on the B2 then the Brennan unit IS correctly working as a NAS. The only limitation of the B2 is that is that the NAS will not be very fast because the computer in the B2 providing the NAS functionality is only a small "credit card sized" Raspberry Pi.
The NAS provided is not something that Brennan have invented/coded, it is a standard Linux NAS.
To make the B2 a NAS do this.
From the front panel and using the round knob (press to select, rotate to choose) go "Main Menu" > "Settings" > "Maintenance" > "Start NAS".
After this the B2 will deliver a NAS to its contents on your Home Network, whenever it is powered up.
Then if you have a Windows 7 PC go into file explorer and you should be able to see the B2's NAS It will be appear as "BRENNANB2\music" and the User ID to access it is "root" and the password is "brennan" - you will be asked for these by windows as you try and connect.
Fred