tsiloics, I'll respectfully disagree with your statement that a custom is only an element of design and not of production.
Interesting questions, CM. Along the same lines, where would a company that sends their blades out to Bos for HT fit in to the equation? Or someone that buys pre-cut blanks?
To me, a true "custom" has no parts that are mass produced. Each part is created by hand by the maker, and is fitted together, one part at a time. This said, I wouldn't expect a custom maker to produce his own G10 or Micarta as an example.
This thread by Josh Smith, and his process, is what I consider a true custom. Alsdorf, Coats, Davison, Voorhies, Clark and others are what I consider true custom makers. Strider and Sebenza aren't what I consider a true custom knife. Very nice, and on the high end of quality, but not a custom when compared to the others I mentioned.