I'm a little unsure about the statement someone quoted from DXV that even a free version of someone else's work is illegal without their permission. I can't imagine it being illegal for me to cut my own Dominion cards for my own use and play them with my friends, as long as I don't try to make money off of it. What part could be illegal? Are the cards themselves contraband because I took someone else's idea to make them? Okay, fine, suppose I don't make the cards and my friends and I just play by writing everything down on a piece of paper. (Say we use a random number generator to resolve shuffles.) Is the paper illegal? Suppose my friends and I have eidetic memory and can simply reproduce the entire game state in our heads, and play by just communicating. Is this action illegal?
Surely this isn't what he meant. He probably meant that if a free version can compete with the official (costing money) version, then there should be laws to protect the market interest of the official version. But is this really true? If the free version competes with the official version, then the official version, well, isn't competitive enough. It has to be made better.
I'm sure we could all make our own standard 52-card playing cards, but they just wouldn't feel the same and Spades or Hearts or whatever wouldn't be as enjoyable. So we spend a couple dollars because it's worth it. We buy Dominion because (1) It's more valuable to us than the time, effort, and result of recreating our own, and (2) We like the product so we want to support those who made it so that they will continue to make good products.
I think that creating a virtual copy of Dominion (like Isotropic was) has to be legal under any sensible laws. In fact, I would probably argue that doing so is a good thing. If the "official" version is not as good as the user-made version, then a law shouldn't protect its existence. The pressure of people using the user-made version instead of the official version should force the official version to become better. Goko is allowed to exist in a state that is unsatisfactory to the Dominion fan base precisely because there is no competition to Goko. As long as the user-made version isn't charging money (because then the copyright owners should be able to sue for that revenue), I don't see the problem. I also don't see how anyone is getting screwed over.