SACD and DSD are being confused here. There's no reason why a player, be it an Oppo, a PC running JRiver or indeed a BDP can't output a DSD download file to a DAC or processor,including over HDMI if that interface is provided.
However, if a DSD stream from a SACD is output over HDMI or any other available interface, my understanding is that some form of copy protection has to be shared between the player and the DAC. I presume the BDA3 offers this, as I am one of those awaiting the BDA3 as a the first SACD capable DAC to use with an Oppo as transport.