Currently, their Velocity program is the only one you can opt into, and, as you pointed out, you have to be an Australian or NZ resident.
There have been rumors that there will be some reciprocity coming relatively soon with Virgin Atlantic.
There is also an interline agreement in place with Northwest Airlines (and I imagine that will be true when DL completes the merger with NW) and with Alaska Airlines. At this point, this doesn't mean much, but a few months ago the CEO of Northwest did say that they will be monitoring V Australia's progress and stronger links may be possible in the future.
I am not sure that Delta, who is about to enter the Australian market in a short few months, is going to want to go forward with any further agreements with a competitor.