Lost!

[bewitched]

Originally Posted by Ghoulish Delight

But that's completely inconsistent with Rousseau's account of Jin disappearing when the flash happened.

Not necessarily. Insofar as I know, the people moving through time on the island are only moving through the past. I have never read anything in this theory (although granted, my knowledge is limited to a layman's study) that says people in the past would experience a time/space traveler as a permanent fixture. In my understanding, all times/spaces already exist as do the people and things in them. Someone moving from their own current universe would only occupy another immutable universe for a fixed period of time before moving on to another, or back to their own universe. I also accept the idea that even if this is the overriding theory that they are using, they are not above tweaking it for their purposes.

Originally Posted by Ghoulish Delight

The "windows are only open for a finite period of time" because the island moves. The room with pendulum tells them, "during the period of time between x & y, the island will be in this location. After time y, the island will move and we don't know where it will be." It has nothing to do with time travel. There has been nothing that says the island itself travels in time, it seems to be moving in space instead.

Parallel universes/multiverses allows for space/time travel. It is still, technically time travel because all times (and places in time) exist at once, including all possible current times. In this theory, the island's movement through space would be the island moving between many possible current times.

[bewitched]

As an aside, if you remember at the Orchid station, on the instruction tape, Marvin Candle said the station sat on a store of "exotic matter". Morris-Thorne wormholes are postulated to be held open (or stable) by a form of "exotic matter".