Can you see from the pic that it's not two windings connected like a series 2?
Fair enough, but it is a single bobbin and does not look DIY but an off the shelf part.
Anyway, here's another guy doing the same thing (and saying he's the only one):
http://www.guitar-mod.com/mm5/merchant.mvc?Screen=PROD&Product_Code=RG_EB3 This second dude has some options including upgrading the choke it to the Novak one (which is humbucking and looks exactly like the Series 2/Ripper) and a passive distortion option a la Jim Lea (push pull pot and some diodes for +$20 - there's a write up of it elsewhere on his site and you can see the pp pot in some of the pics) except on the mudbucker only vs master (not sure how Lea had it). And paper in oil caps (avoid; not worth it). Can't quite tell from the pics what the 'stock 'choke is, but you can see that he wastes money on 600V orange drops (or the MOD brand equivalent, depending on the option - that's charging customers more for no good reason and due to the value of the mudbucker tone cap it is commically large so it has to sit in between to tone pots vs on top like the minibucker and just about every other tone cap you have ever seen). I know, if people want orange drops that's how they gonna come; but it's still stupid to use larger and more expensive caps designed for use in tube amps as coupling between gain stages, as a guitar tone cap. In a blind test you wouldn't be able to tell the diff between that and a 50c box film (a quality one) and there are many other options, including other, more appropriately sized, polypropelene caps (like the Orange drops). I also don't get why he puts weird connectors on the leads - those large O things are not appealing at all. Weird mix of modern and cloth wire too. But other than that they look well done (if cramped). Anyway more description of his circuit and sound samples here:
http://www.guitar-mod.com/rg_eb3.html