Interesting. What are the differences, legal and financial, between LDS building a publicly released design to GB spec for profit and an Authorized Builder doing the same?
LDS will not build a 'fEARful' cab. Way early in this whole thing, before there were authorized builders, he built a few cabs loosely based on the fEARful plans, but put in his own changes and preferences, which made some customers happy and others disappointed. So, he doesn't do that anymore.
However, the fEARful cabs use stock drivers. Just like the 212's, 410's, 110's, 610's, etc., etc., etc., Don has made mid driver loaded cabs for many, many years. He has one of the best crossover designers in the business IMO (Ralf Patterson), and his version of the 12/6 and 15/6 cabs based on the stock LF drivers and various other stock midrange drivers sound very good to me. He is one of the best woodworkers and Tolex guys in the business also. The fEARful authorized builders seem to do a very good job also... some beautiful stuff coming out of those shops also.
His 12/6 build, with the 3012LF driver, rear porting (to keep the size small) and the beautiful sounding Faital mid driver, crossed over a bit higher than the standard fEARful crossover is the best sounding 12/6 I have heard to date.
There is nothing particularly proprietary about tuning a box for an LF driver, and then crossing over a nice mid driver, just like there is nothing particularly proprietary about putting four 10's and a tweeter in a square box. That being said, if you want an Epifani 410 or a Berg 212 or a fEARful 15/6, you will need to buy that exact thing from those companies.
Edit: That all being said, the new fEARless 212 looks killer. Love that spec.... one cab that can handle almost any gig, 4ohms/high sensitivity, relatively small, powerful. I'd enjoy hearing that one!