I haven't heard of tapmaster before, but tapster is a bartender (the one who controls taps of barrels cointaning alcoholic beverage). I think it means the same.

I'm not sure it's an established word; I think the author might have made it up. "Tap" refers to a beer tap (http://en.wikipedia.org/wiki/Beer_tap). So this "tapmaster" is either the owner of the tavern or an employee who serves beer. That is my best guess! I've never seen the word before.

In your example it means the person in charge.

Tap Meister [slang]: "Meister" is a German word, has been borrowed into English slang where it is used in compound nouns. A person referred to as “Meister” is one who has extensive practical skills in his profession and business. In this context it is referring to the person pouring beer and most likely the tavern owner.

Thanks. My choice is"taverneiro" (in Portuguese, the owner of a tavern").