If one prints copy of "this same poem" and sells it or distribute if for free (and there is no free lunch) then one stole the printing rights that the author granted (for a sum of money or a regular paycheck) to the official printer (the one who has a contract with the author). Regarding books, ideas are more or less free, the materialization of that work of thought into our physical realm (be it dead pieces of cellulose or bits on magnetic support), however, is not.

Kant wrote a bit about it.