I have never run across the document you're referring to, but I would think that whoever wrote it was praying to whichever god she/he worships in regards to whatever religion she/he follows. It could easily be God of Christianity or a pagan god or goddess. It still doesn't make BDSM a religion.
There are some parts of Christianity that are pretty scary if you think about it and sound a lot like D/s. A wife is commanded to submit to her husband in all things. Women are not to speak out in church and risk embarrassing their husbands with their ignorance but are told to wait and ask their husbands. It is suggested that we should go into a dark closet to pray.
The slave versus sub debate is a whole other topic that you'd probably find plenty of answers to if you use the "search" function.