When I watched The End for the first time, I had an immediate understanding of the show that worked beautifully for me and still remains my interpretation of it. I say this because to give an "interpretation" of something that is meant to be interpretable seems to imply some sort of pre-meditation or devising on my part, but this interpretation is my UNDERSTANDING of the end of Lost, in that it occured to me, or in me, in the moment of the show; it was not an afterthought of me trying to work it out later.
In another disclaimer, I would like to add that I have no idea if this interpretation, by the general standards of Lostpedians, is obvious or crazy or somewhere in between. At first I thought it was obvious, but when I commented on the blogs after The End aired, some people bluntly disagreed with the conception I was working with. In any case, I acknowledge that this is my interpretation and that there is a vast array of others (which I would like to hear!).
The Flash Sideways was real. It wasn't a metaphysical afterlife or purgatory or some divine test; it was reality. What Jack and Faraday wanted to do in The Variable worked in The Incident, and the effects were displayed throughout season 6. Detective James Ford and Dr. Ben Linus and all the rest were real people who were born by real parents and had a real childhood and lived through real histories.
These histories were not happening at the same time as the ones in the OT. Time becomes a relative thing; both of these (I'll call them) places aren't two 2-dimensional lines that have perpendicular lines between OT 2004 and FST 2004, OT 1977 and FST 1977, etc. Between these two realities, there is no BEFORE or AFTER or DURING. They are not like two different snails moving along a sidewalk, leaving sticky lines behind them. They are like ONE snail that is actually two different versions of itself; they are both the snail AND the sticky lines it has made AND the sticky lines it will make.
So in OT, James Ford lived his entire life and made extremely powerful connections, the strongest of which was his relationship with Juliet. In FST, he came in contact with Juliet and he "awakened" to his other history. It is not like one James Ford X was invaded by James Ford Prime; there is ONE James Ford, who awakens to the fact that the history he has percieved and remembers is not the only history James Ford has percieved and remembered. The way this happens, the way it happened for ALL of them in the FST, is that they came across such resonant and powerful connections and moments and emotions in the OT, that the people that have lived through the history of the FST are able to awaken to or realize that "other life" by coming into contact with things associated with those resonances and connections and people.
The fact that they "moved on" is one of those things that I don't have or need an answer to. I interpreted it as one of those things that aren't supposed to be an extension of the reality of the show, but a cap-off to the beautiful emotional ending of Lost; a final enigmatic testament to and continuation of the emotional resonances up to that point. It was the last word that unteathered the show from its science fiction/drama restraints and let it fly into unknown territory. I think that any theory or interpretation that attempts to resolve or quantify the "moving on" will not only fail, but will miss its point and purpose.
Please share your thoughts and interpretations! I know it's hard these days to find anything to talk about on here other than (delightful) favorite lists and such, and this blog was party an attempt to revive some last strain of the conversation that happened before the show ended, and also just to get my understanding of the show out there and see what people think of it.