I do think it is only fair for supporters to get first pick, there will be a demo for everybody too just a little later. That aside netkar really is a steal, the hillclimb alone is worth the 15 euro you pay for digital download (7 euro for boxed version plus shipping)
The reason why the first technology preview is license based is so that they can test the functionality of their license checking system. Take it like a demo of LFS with only S2 content available. So you can download the demo without any code, but actually playing it requires a code.
I remember nKPro having a weird license system, where you could launch any track with any car, but the car just didn't start without a code entered while starting up the game, you could walk around the track but no driving was allowed. Of course it had demo content where you could drive the formula1600 offline. AC might be similar in that regard, but i doubt it since they said it's a different system altogether.
I will add this quote for the third time in this thread:
as you might know, Kunos Simulazioni is producing "Assetto Corsa" a new racing game for PC Windows: Because in the past you showed interest in our new project, today we are glad to offer you our "Assetto Corsa Technology Preview" before the public release."