Based on what I read in the MK moonlight magic threads, the system will NOT recognize a non-DVC reservation, and will NOT email the link. But anyone with an on-site reservation is eligible to book starting tomorrow.
I have a two night DVC stay at Boardwalk, followed by an RCI exchange into Saratoga Springs in mid-March. Our moonlight magic night falls into the SSR portion of the trip, so I'm fully expecting to have to call to make my reservation, and probably explain to the CM *why* I had to call (since some were being told that they must use the invitation-only link for the MK event). Unless, of course, they've fixed this. But I'm not hopeful.