Will 1 key work for both Windows and Linux?

Will I be able to get both the windows and the linux version for the price of one, or do I have to buy it twice?

Good question!

Same about mac, too!

And what about Steam keys when/if the game is out on Steam?

At least steam should work as a key is bound to your account and not your computer if i'm not mistaken.

It would only make sense that the same is true for the ubernet and in the end the gameclient itself will not be drm protected so one should be able to gather a working copy

I think the point is that your key is your login. I see no reason why this shouldn't work.

I imagine that keys will not be platform specific. There really isn't any reason for them to be. Making platform specific keys just makes more work for the guys at Uber. Besides if you buy the game in a store how are they supposed to know what OS you run at home?

No, there are multiple keys associated with your account (e.g. for DLC, Addons, Special Custom Commanders, etc.). Keys have nothing to do with logins, and neither should they.

Confirmed on stream that you can play from multiple OS's with 1 key.

Well what I gathered from the live stream Q&A gmorgan was on the money.

One account per key. SupCom-Style?

I think it is fine. Stops people from making 20 smurfs for free, while at the same time you can make yourself a smurf or two...