Is this new with 1.04? Because I know DirtySanchez made a community map pack but could never get people to d/l it to use them - everyone needed to d/l it to all play together.
Are you referring to the in-game map designer or Galaxy Forge maps?
The tool you use to make the maps is really irrelevant, I would say I use notepad just as much as the official tools for map making, and the game doesn't care either. DirtySanchez's map pack was of fixed maps, indeed made in Galaxy Forge, and those cannot be autodownloaded. This thread and my posts are about Random maps, which made in map designer or not, can be played with only the host having the map (sadly the players do not keep these maps afterwards), and it has been this way since Sins was launched.
Regardless of whether Stardock will include more random maps, my point was just that nothing is stopping the multiplayer community from making their own random maps that will on average be fairer or more interesting. If Dirty's map pack was of random maps, I think it would have had more success, as once it was distributed to the major hosts, it would spread by word of mouth and become standard.