Its the other way round, plug renamed to bifferboard. It seems to me that this plug is just a NAS-device, called WANSER-R (Biff has set a link to it on his page, under "buy"). This device just provides network storage. Fine, but bifferboard is much more, a linux computer with GPIO, serial- and i2c-interface, which can do many things, including network storage.
Its the merits of Biff, the original supplier of bifferboard, that WANSER-R became bifferboard, with a new bootloader, fitted linux kernel and many other hacks that make the many applications of bifferboard.