It's kind of wierd though, you obviously need internet to access it the first time you log in... but when my internet hasn't been connected I have still been able to play sometimes. It is very trial and error though and might just be a bug.
If you have no internet connection it will come up with 1 of a few different errors, but every 1 in 10 tries I have been able to get into the game without needing internet. Very strange indeed.
The required online authentication is the only feasible way to do copy protection when there's a new build every day. The final game is too far off for the method of copy protection to have been discussed yet, but whatever it is it will support offline users.
Also I've tried starting the game offline in my current build (189) and hasn't worked so far. So the bug has been fixed as far as I can tell.
I still agree with the online only part while in development... It is almost guarranteed that it will be offline aswell once is is either completed or even near enough to completed.