Against my better judgment I'm going to offer my opinion.
I am the father of two kids from a previous marriage, and to the best of my knowledge they are my children. I say this because I have not had blood tests done, but they sure look like me, except much cuter.
I can see both sides of the picture here, and to a degree I agree with both, but not entirely on any side of the debate. Since the children have only ever known one father, I understand why the judge ruled in favor of the mother. If my children turned out not to be mine, I do not think I could love them any less and I would continue paying the support. I say this because even if I am not the sperm donor, they are MY kids and I have raised them according to my values and principles. I love them as MY children, and I always will.
That being said, I would launch the mother of all civil suits against the mother, and have her charged with fraud and every other thing I possibly could. To play someone to that extent is just plain evil, there is no other word for it. I can't even imagine discovering that my past 'X' number of years has been a fraud, and that I have been played for money.
Oh, but the money goes to the kids people would say. Bullshit! I can say without a doubt that the thousands of dollars I pay a year does not entirely go to the children. It goes to increase the standard of living of my ex-wife indirectly through my children. I have never had to option to provide formula, diapers, clothing, food or anything else that goes directly to the children. What I have done is pay for a house that is larger than my kids need, vacations for the ex-wife that she would not otherwise be able to afford, and meals out at least three times a week. Remember, the person getting support does NOT have to explain where the money is being spent.
This to me is where the issue is. I would have NO PROBLEM paying half the amount of support to my ex-wife and the other half going into an RESP for the kids. And I would have no problem of receipts were provided showing where the money is going to. All I can say is that when we were together, the kids did not cost a fraction of what I was paying, and that is not including the money she is getting from the government being a single parent, and the extra amount I pay for extra carricular activities and daycare.
But enough of that vent.
Yes, it is fraud by using the children to artificially increase ones standard of living, and the woman should be punished accordingly, both through charges of fraud, and through a very large civil legal suit.