Acronym misery, I agree, but there are two doubled rope methods, not double rope as Corey states above- that would be using two seperate lines (two ropes), hence 'double'. Doubled is the same rope, one side going up, the other side going down. That's where we get the Dd in DdRT
Of the two doubled rope methods, the one far more extensively used in Arboriculture is the 2:1, friction hitch system, with or without a split tail, this has been coined DdRT, even in the Sherrill catalogs. The two sides of the rope move opposite directions, relative to one another. There is motion and friction at the crotch-over point.
The other doubled rope method, the nearly unknown and non-existant DbRT, I assume, gets the 'b' from the middle letter of the word 'doubled'. That's my best guess, anyway. In this one, both ends of the rope stay on the ground. A backed-up dual ascender gets you up the rope, or a prussik, a la the thread starter's guy (if you have balls that size). Once up, the ascenders come off, friction control is put on and you work the rope on the two, parallel lines, both ends still staying on the ground and no rope travel (ie, no friction) at the tie-in point. All friction control comes from in front of you, just like in SRT. This is done with some sort of device.
Hope that clarifies, crystal clear. The problem, still, is the nomenclature, what to call them, how to term them. I'm not sure we have the liberty to go and decide and change names here, but I'm in agreement that the DdRT - DbRT thing is very confusing.
MDRT is a really good name, I think, and the acronym says more clearly what that rope technique involves; motion. The rope sides move up and down as you move upo and down.
For the other,I like 'static doubled rope' as the rope is static, from the motion sense, but that allows confusion that one might think it involves a static climbing rope (in contrast to a dynamic or semi-static), which it can, but any type of rope can be used. This would be SDRT.
Our conventional DdRT would be MDRT, the lesser known doubled rope method would be SDRT and then the unambiguous SRT. SDRT and MDRT would more clearly describe the two doubled rope methods, but at the same time, very, very, very few climb the 1:1 doubled rope method. The naming of this lesser method is more to keep in frame that it does exist. SDRT might be read as 'Single Doubled Rope Technique' which is actually OK as the actual handling of the rope is identical to SRT, only you you have the two lines going through friction control instead of just one.
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I for one love the idea, no more do I go cross eyed trying to decipher the two. So much easier to visualize, it lowers my bloood presure just thinking about it 
lol
“Get him.” lol
