At first, I kind of laughed at it. Then I wondered whether anyone actually used it. Then I considered whether I would ever use it as a parent.
The long and short of it is, "NO."
As an atheist, I don't like the idea of indoctrinating children. I personally find the fact that many (if not most) children are brought up in a faith, believing that that faith is the capital-t Truth, and that to question that faith is to reserve oneself a spot in hell to be utterly repulsive. I am still angry about my own religious upbringing and the horrible guilt that I went through (and, in some cases, am still fighting through) as I left the Catholic faith. Indoctrination is a Bad Thing, capital letters and all.
Reading about something on the internet is not indoctrination. If I blocked my children (not that I have any at the moment) from reading religious content on the internet, I'd be no better than my parents when they threw a fit about my not going to church. I'd be no better than my sister, who was irritated when she had to read a book by a prominent atheist for a class in her first semester at university. I'd be no better than my high school, which blocked access to webpages related to LGBT issues and refused to allow students to start a Gay-Straight Alliance organization.
Blocking a selection of sites because they contain religious material doesn't make the problem of religion go away. In fact, blocking out religion may make children more easily led down the path of superstition when they do encounter it -- and they will encounter it, eventually. Children don't benefit from adults putting blinders on them; they benefit from adults explaining things, and answering their questions, and helping them understand reality and truth and justice and morality and humanity.
Children don't need to be protected from the knowledge of religion. They need to be protected from indoctrination, yes, but any child who grows up in a home that would consider installing this thing is unlikely to be at risk for indoctrination.
I remember, when I was in the eighth grade, being asked by one of the school librarians (I shelved books after school -- and sometimes during civics class -- and was quite chummy with the librarians, as they let me have whichever books I wanted, whenever I wanted, for however long I liked, in whatever quantity I pleased, regardless of whether the books had even been processed for checking out yet) whether I thought Philip Pullman's His Dark Materials trilogy was appropriate for the twelve-to-fourteen-year-old audience of the school, in the face of some parent having requested that the series be removed. Having read the books a few times, and in the middle of my own realization of disbelief, I replied with something along the lines of, "Well, if people can't defend their religious beliefs against a story, then their beliefs aren't worth much, are they? They'll never have strong religious beliefs if their beliefs are never challenged."
I feel the same way to this day, and I feel the same way about atheist kids. A kid isn't really an atheist if she knows nothing about religion, and she also has no way to defend herself from its lies if she's never told about them. A girl or boy who can be converted to a religion based solely on what she or he reads online is a child who has not been properly educated about science or about religion.
So if/when I have kids, I will definitely not be installing GodBlock or anything like it. I will be buying a copy of the Torah, and of the Quran, and of the Vedas and the Noble Eightfold Path and whatever I can find on Norse and Roman and Greek and whatever else mythology, and I will put these books with my Bible(s) where my children can access them, perhaps in close proximity to an encyclopedia and a dictionary and some books on basic scientific principles. I want my children to know about religion. I want them to understand that over time many people have believed many things, and that these beliefs conflict. I want them to be able to see for themselves that none of these religions truly explain the world.
I don't want to blind children to what people believe. I don't want them to disbelieve on my authority. I want them to understand, and if they choose to reject religion, to do so because it is the conclusion they have come to by examining the evidence, and not because it is the only viewpoint to which they have been exposed.