Just a few thoughts...
I don't think it mattered if Jenny died or not. The story could of been about any kind of love as long as the love seemed eternal. Death made that work best I guess.
The purpose of this story was to send a message. Love is transcendent, love is...something that happens and we can't help it.
It almost seems Brechtian, in that this movie was teaching a lesson before anything else. Once more, it even dissed the constrains of capitalism with Oliver disowning his father. Another Brechtian thing about it was the directing. If you notice, the camera focuses on Oliver's face when thinking about Jenny dying. While it may of had an adverse affect by making things too emotional, it also worked in Brechtian terms by pushing the actor on us rather than puling away in some panaramic view. The shot of Oliver and Jenny at her death bed was shown at a distance though and that was definately Brechtian, because the death needed to be as distant as possible for it to be put in proper perspective with the message...which is love. It is tough to do a movie about an emotion like love and try and seperate the other emotions from the matter. Frankly, I think doing that just sends the message that we are stupid and need one thing spooned to us at a time. But hey, I can appricriate being called dumb!
By the way, I just loved this movie!