It is using the MAX485, just the PCB is designed to connect it to Arduino Pro Mini by pin headers. The goal is to get small programmable device which can be connected to a bus network. This device could be used in low cost decentralized home automation project. Basically it is the same as popular breakout board for MAX485 (like this), but modified to have smaller footprint and two screw terminals for connecting to the bus. It also has a jumper for termination resistor and the enable signals can be configured by solder jumpers.