Nippon 2007, like all Worldcons, has limited resources and many demands on these resources. Therefore while the GOH’s and their spouses, the Hugo Award Winners, and the Seiun Award Winners will be provided tickets for Donbura-con, everyone else will have to pay if they wish to join the dinner cruise. Yes, we’ll figure out refunds if someone purchases a ticket for Donbura-con and then wins. (More likely, we’ll arrange a transfer with the new person re-paying the Hugo/Seiun Award Winner for the ticket.)
Note that, as above, only GOH’s spouses’ tickets are included the complimentary tickets, not the spouses of Hugo Award Winners or Seiun Award Winners. While we would love to treat everyone one associated with working on the Worldcon in any way, acceptors, presenters (and their significant others), all other committee, program participants, staff, and volunteers are on their own last time there was a conversation about this that I was involved with.
If it were me, I would do what I have in fact done, and purchase my own tickets for Donbura-con.
If further clarification becomes available, we'll publish it here.