I understand it will be free, even for pirated copies of 7 & 8. The trouble is of course it will fail activation on a pirate update. A recent magazine states Microsoft have said they will offer windows 10 for cases where it won't activate at a reduced cost. To me this seems to be an incentive for people to pirate a win 7 or 8 copy to qualify for a cheaper copy of win 10 where they otherwise would not have qualified at all before?
Updates to 10 are said to be free for win 7 & 8 users for one year from the release of 10, and I for one will not be in any rush to be a Microsoft Kamikaze test pilot. Let the dust settle, and I also can't see the reason for a bloody icon to remind me, which is Microsoft Spam.
If you don't want the Microsoft spam, remove KB3035583 from your installed updates, and then when you see it in the list of new update downloads, HIDE IT. See some people are saying Microsoft have tagged KB3035583 as an "important" update.