Sure UBL wants Bush to win, so he can kill off the remaining 25% of UBL's merry band. Sure he does.
The reason the North Vietnamese were using the VVAW and John Kerry in 1970-73 was because they needed Nixon to at least lighten up on them so they could recover from their combat losses. This may be UBL's play to get a guy in there who's less serious, and maybe be able to rebuild the organization. Al-Qaeda is still terribly dangerous, but it's in awful shape compared to 9/03.
Elect Kerry so UBL can rebuild his forces to strike another day.