The BMD-300-EVAL uses the same debugger firmware as Nordic's nRF52 DK board: Segger J-Link-OB.
Hardware flow control on the debugger's COM port gets enabled through a hardware method that common terminal programs (e.g. TeraTerm, Putty) can't handle. Please refer to this link on Nordic's DevZone forum for additional information.
We provide a reference design for a break-out board with the BMD-300 and a FTDI FT230X USB-UART. This has a DIP form factor for use with breadboards:
Design files in Eagle are here: http://www.rigado.com/?wpdmdl=1297
The bare PCB is available through OSHpark: https://oshpark.com/shared_projects/Rc30UPCT