Well to be fair, Halo is so bloody derivitive that anything in the same genere is going to be a lot like it, almost every non-modern FPS is called a Halo clone, just as modern FPS games are called CoD clones (deserving or not in both cases). Bungie makes a specific type of game and apparently isn't going outside of their specialty, so the similarities shouldn't be surprising.
The big question I have though is that with them no longer controlling the Halo Liscence, how much proprietary design and tech went along with it. I've been wondering for a while if Bungie was going to get a boom lowered on it near the finish line to knock them out of the competition despite everything seemingly being friendly. Waiting until the last moment and all the dev money was spent would be the most damaging way to do it. Only time will tell.
I'm a pessimist though, I tend to consider the worst, and most sleazy, possible outcomes. To be honest I'm actually surprised when I see a company part ways with a bigger company to do the same basic thing and become the competition. I always look for the kind of bickering we saw with the various home band games, slap fighting over who owned what tech, and developed what under which liscence, and whether say a plastic mock-turntable for a video game console should be fairly considered generic or a proprietary technology. If Bungie routinely uses some very similar code and ways of doing things, it could be intresting if it's argued that code went with Halo and duplicated their previous techniques was a violation of the liscence they sold.