Man why are some people so butthurt over this? Companies have been ripping each other off since the inception of Pong. There's nothing wrong with taking a bunch of good ideas and adding your own little flavor to it. Sure, there are blatant ripoffs but we cannot deduct that from the trailer provided. Hell, lets look at some successful rip offs that nobody seems to notice:
Halo: Rips off every FPS before it.
Guitar Hero and Rockband: Rips off Guitar Freaks, an arcade game from Konami.
Call of Duty: Rides the wave of success made by the Metal of Honor and Battlefield series.
Saints Row: One of the more successful GTA rip offs.
And you know what? A lot of people enjoy these games. H.A.V.E. appears to borrow a lot of ideas from TF2, but who says it's going to be exactly the same? All the classes from TF2 aren't there, it's in third person. I donno, it looks okay. Who knows? Maybe it'll be a good alternative to other class based shooters.