Snowman is correct. The GT-R that is sold in the US comes with the same warning message as indicated in the above letter. You actually have to sit down with the General Manager and sign a series of documents stating you understand the tranny and other mechanical devices in the car make noise and not to be worry about it (i.e.: don't be bringing the car back in for servicing for every noise you hear). You have to go through a full checklist of things with the dealer as he explains everything about the car to you. They have to tell you there is no launch control, but in fact they give you a little 'wink and nod'.
When it comes to the warranty, the way it is understood (and explained to me by my mechanic) is that if you turn the VDC off, AND break some aspect of the driveline, they will argue you are abusing it. IF you turn the VDC off, beat on the car, turn it back on and shortly afterwards something happens to the driveline; they will check the black boxes and if they see the VDC was turned off for any period of time, they will consider voiding the driveline warranty. In a letter to all dealers in the US, Nissan North America issued a statement saying basically they would only void a warranty if they saw clear abuse of the car (i.e. doing something explicitly against what is in the manual).
So the key is black boxes and how long they record the activities on the car and if you are engaging in an activity that is expressly prohibited in the manual. Nowhere in the manual does it say you CAN'T use launch control, because it is not a feature they document. BUT it clearly states that turning VDC off for anything more then getting out of snow/mud will void your driveline warranty if something breaks BECAUSE OF THAT SPECIFIC ACTION. For you everyday driver these conditions should be fine unless you are beating the crap out of the car on the street. (I don't see people setting up the car for a LC at every stoplight, just not practical) For guys who are tracking and want to remove as many electronic nannies as possible, this poses a problem and needs to be thought out before you go turning off the VDC for the track.
Again, this is a perspective from a US owner. I can't for sure say these rules will apply to Australia, but I would assume it would be very similar.