I would imagine it is exactly the DNC that Seth's family is afraid of. As it has been pointed out, the family was immediately surrounded by DNC lawyers, who would have been very clear about further consequences to living gamily members. In my opinion Assange has already told us Seth was involved in an earlier iterview where he was asked directly if Seth was the source. His words were 'I'm not going to divulge my sources." But he looked directly at the camera and nodded 'yes' while saying those words. Donna Brazille wasn't at the same hospital as Seth, in the middle of the night, visiting friends. This was a high-priority situation that required personal attention.