Personally, I don't feel that Minecraft getting inspired by Dwarf Fortress, Dungeon Keeper, and Infiniminer is really as bad as the "inspiration" that FortressCraft got from Minecraft. For one, Infiniminer is open source, so that negates part of one of your points, Mr. Video. That is also the only part that, in my opinion, really is the essence of Minecraft. Infiniminer is all about the mining aspect, almost like Dig Dug in the way that you just want to dig. Minecraft is much more than that. The whole open world aspect of it is enough on its own to make this point clear. Yes, the core points of Minecraft are the build/destroy aspects, but this is not exclusive to Infiniminer. Any sand game has these parts, hell, LEGO did it way before any of these.
My second point is the fact that nobody seems to do their research. Now, I haven't read the rest of the comments, but just looking at the first pages I can assume how it goes. Nobody wants to bring up any new points. Well, here's one: Dwarf Fortress looks and plays NOTHING like Minecraft. One, its top-down, and to an extent it looks text based. The inspiration from this for Minecraft is most likely the open world environment, where the world changes every time you play.
Finally, Dungeon Keeper. Yes, it involves monsters, and loot, and such. But, like Infiniminer, it doesn't have any overworld elements. Its the overworld of Minecraft that people fall in love with, like seeing your first waterfall or cliff. And please don't tell me that the idea of dungeon enemies is original. It really isn't.
The last thing that people miss is the age of some of these inspired games. Yes, Dwarf Fortress is still being updated, but both Infiniminer and Dungeon Keeper are gone. Nobody plays these games anymore, and that's what makes it more acceptable to take concepts from them. Minecraft is still around in a large number, and its not even out of Beta. The anger doesn't really come from the concepts they share, although that is a large part of it. The anger comes from the fact that Minecraft isn't even out entirely yet; and that this looks to be just someone trying to piggyback onto the viral fame that Minecraft that has created.
Also, I'm not against FortressCraft's existence, I think competition is good. But i do think it should have brought more to the table.