It's still a bit vague. If you piece together certain bits of info, namely that:
a) boxed editions won't use the steam DRM
b) the in-game server browser is using steam
it looks as if you can install and activate just fine without Steam, but that will only give you the single-player mode.
To fly in multiplayer you will need to install steam. Alternatively, you could wait for a different server browser to add support for CoD which, due to the popularity of the title, wouldn't take long. That is assuming it can be ran though an independent server browser, which Oleg Maddox confirmed at some point, but the constant back and forth of conflicting information is making people doubtful.
To be honest i trust the guy, so if he says that it works with 3rd party server browsers it most probably will. Maybe not on day one but down the line a bit. In any case, i'm in no hurry to fly multiplayer for a variety of reasons, so i have no problem waiting a month or two.
I'll be getting the game when a relative returns from the UK for holidays, so it's going to be about 2 weeks later than release. Then, the staggered release means there will not yet be a North/South American community to fly with, neither will their servers, for a few more days.
Finally, assuming there are enough European servers it will take some time for mission builders to get to grips with the FMB's best features. It could be some time (maybe a week or two) before we get realistic and well-researched missions with triggers, or the much anticipated online mini-campaign running on any servers. Not to mention that many people will probably be hosting with complex engine management disabled initially
In that time frame, i'm going to get acquainted with the bits and pieces of it in offline mode. I'll do the Tiger Moth training, then try all the aircraft in the QMB and finally i'll start the single player campaigns and try to complete both, possibly making some sample missions of my own for the aircraft that are not represented in the stock campaign.
Until i'm done with all that, it's highly possible that if external software can substitute steam for CoD matchmaking it will have added CoD support by that point in time. Not that i'm much of an online player anyway, it might be weeks or even months until i get the urge to fly in multiplayer.