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Sorry, but I can't quite understand your statement "Buying additional desktop copies won't get you more e-files."

What is the difference between me buying two copies and installing them on two computers vs me buying one and my neighbor buying one?  How is the 5 e-file limit enforced if not per copy of TTAX?  What exactly does the "you" refer to in the statement "won't get you more e-files"?  What ties the 2nd copy of TTAX  that  I  buy to the 1st copy that  I   buy?