INCINERATION! This game is heresy. I can tell by some of the pixels and from seing quite a few heresies in my time.
Because it has references and trademarks (such as the Chaos marine) from Warhammer 40k, and that game doesn't have a licence from Games Workshop to use those trademarks.
I don't see it. Unless entities within battle armor and the color red are trademarks of GW, I don't see anything wrong.
Even though your probably don't see it, the uploader of the video did: "Let's Play Downgate Exodrone Wars: Xbox 360 indie game Downgate Exodrone Wars is a blocky Minecraft-looking shooter with Space Marine-looking space marines. Watch Andy and Jane play in this Downgate Exodrone Wars gameplay. " This is put in the description of the video, by the way. But still, the units in the game look similar to the ones in Warhammer 40k, which could be intentional to use the popularity of W40k to increase the popularity of Exodrone wars. After all, the majority of us would assume it's related to W40k, by just looking at the video and seeing space marines. Considering we are fans of the franchise we would be more likely to buy the game compared to if it didn't have those look alike space marine units. And that's kind of the reason why GW would be likely to sue the creator of the game...
A person's personal opinion does not count. Even if he called it "look at this WH40k copy". There are no "Space Marines" in the video. The characters are robots. Even if they were organic, a creature in battle-armor is not "copying" WH40k. You can't copyright the idea of battle-armor. The majority of users would not confuse it with a wh40k game, because those are robots. If people buy the game thinking it is a wh40k game, then they are not too bright to be honest.