Here is what Marcin said:
“We were totally overwhelmed because, honestly, we were not expecting such a degree of success. But sales-wise, The Witcher series has sold over 20 million worldwide, out of which almost half of it is from The Witcher 3. So we practically doubled the sales of the series.
Generally I think with The Witcher 3, and it was the case with The Witcher 2 as well, we released our game without any copy protection. So on day-one you could download the game from GOG and give it to a friend – enemy as well – but give it to a friend, on a memory stick, it works. And still we sold near to 10 million copies across all three platforms.”
Congrats to these guys! I still play The Witcher 3 since it came out and I love it. All of the big companies should learn from them, you don’t need a bad ass copy protection to earn millions, your game just has to be good.