From what I've read so far, I don't think the game will keep track of how you have changed the seed-generated world you happen to be on, except in your own client and while you still have it loaded. I don't think the game will have a means for you to load a world that others have modified, other than information like names and the location of planets and what resources it has (in general). I think that they even mentioned that if you leave the planet and then return to it later that any changes you made the first time will not be saved and the planet will simply re-generate from the seed again. In fact, my guess is that due to the limits of having the game generated in this way, that even if I gave you coordinates to a planet I'm currently on you wouldn't be able to see me because the game will have to generate the planet for you from the seed but they don't have a means (currently) to let you load my own "Seed + Changes" version of the planet.
But that's just my impression so far, and I could be wrong.