No, glycerine is byproduct. You get it whether you make soap or biodiesel. If you use water (or lye only) fat makes soap + glycerine, but if you use methoxide (which is lye + alcohol) then you get biodiesel + glycerine, but no soap. Soap is an incidental byproduct of biodiesel manufacture, when your grease is very wet, or has free fatty acids. Some biodiesel preps use sulfuric acid in the first step, which reduces the yield of soap and increases the yield of biodiesel, at the expense of using an additional step, and the hassle of dealing with sulfuric acid which is pretty nasty. But then you can use really rank grease and still get good biodiesel.
So...what do you do with the glycerine?
The “soap” takes a bit more work than just draining from the biodiesel, but the glycerin can be used in any stage after being de-methed (don't want to be exposed to the methanol). As stated, methanol removal is prime but also water, heat, and additional lye is needed for proper saponification.
One other thing - the liquid glycerin soap will clean glass better than anything I've ever found.