I use this
for calculating several factors in my beer, others will say they use Brewsmith, but it is not ported to Linux yet.
Brown sugar will change the flavor of the finished beer. I've used flaked corn, corn sugar (dextrose) and table sugar for added alcohol when needed. Unless you are doing an Imperial India Pale Ale (or other gigantic style beer), you probably will not bump into the alcohol tolerance for the yeast.