In February, I mentioned that the OED's citations for "pirate" as unauthorized publisher go back to 1603.
But I looked up that earliest citation, from Thomas Dekker's The Wonderful Year. The cited passage occurs in a foreword "to the reader." It's an entertaining rant; I recommend the whole thing. It's hard to excerpt without doing violence to the whole, but here goes:
Alas, poore wenches (the nine Muses!) how much are you wrongd, to haue such a number of Bastards lying vpo[n] your hands? But turne them out a begging; or if you cannot be rid of their Riming company (as I thinke it will be very hard) then lay your heauie and immortall curse vpon them, that whatsoeuer they weaue (in the motley-loome of their rustie pates) may like a beggers cloake, be full of stolne patches, and yet neuer a patch like one another, that it may be such true lamentable stuffe, that any honest Christian may be sory to see it. Banish these Word-pirates, (you sacred mistresses of learning) into the gulfe of Barbarisme: doome them euerlastingly to liue among dunces: let them not once lick their lips at the Thespian bowle, but onely be glad (and thanke Apollo for it too) if hereafter (as hitherto they haue alwayes) they may quench their poeticall thirst with small beere.
I can't be sure I'm following everything in the Elizabethan English (and the Latin) fraught with both contemporary and classical allusions. But it really seems as if it's hack writers whom Dekker is characterizing as Word-pirates. I think it's an early day complaint that idiot readers are consuming trashy bestsellers instead of recognizing his artistic genius, not an early day complaint about IP violators.