MultiGo says, it can read bdx files, but which program writes these files and - how do they look inside?
I found a hint:
which translates (by google):
BDX: Breeze and Yi cheng software chess file
What software (weiqi) are these? ... asks RueLue
The Chinese text simply says: Go kifu software by Qingfeng (site now defunct) and Yicheng ( http://www.eweiqi.com/).