The Skreddy Pedals BC109 FUZZ is made from silicon transistors for power and temperature stability, but it's darkened so you can get germanium-ish effects out of it too.
The 2 transistors are piggybacked for better tone (smoother, lower noise than single transistors), giving this circuit 4 transistors total.
The extra controls let you emulate different classic fuzz tones from the 60's and early 70's along with improvements for some of the issues those early fuzzes had (noise reduction, adjustable tone, and input impedance selector switch). Can get frazzly or smooth, bright or dark.
About the name BC109 FUZZ:
It refers to the part number of the transistors used and is certainly not a unique moniker. In fact it's so generic it cannot be used as a trademark; that would be like claiming to own the terms "V8" or "327" as the name of an automobile model. There are other products already out there using "BC109" as their name or part of their name (I know of at least 3 others, not to mention several other products named "BC108"). If you want to use the transistor part designation of your fuzz as its name too, nobody's gonna stop ya. Or you could think up a unique name. Either way is fine with me.