IT appears Motong Has made a knock off of the surface cover. It appears to be Bluetooth because Microsoft holds the patent for the keyboard connection.
Amazon.com: MOTONG Wireless Bluetooth Keyboard Type Cover for Microsoft Surface 3 Detachable Removable ABS with Touch Pad,Black: Computers & Accessories
Amazon.com: MOTONG Wireless Bluetooth Keyboard Type Cover for Microsoft Surface 3 Detachable Removable ABS with Touch Pad,Black: Computers & Accessories