Man, I hope this new Fire Emblem get's a US release, as it might push me to finally get a 3DS.

Seeing how it won't be a remake of an 20-year old game (that still played like a 20-year old game), I have high hopes for this to be released stateside.

If the DLC is free and available from day 1, why make it DLC to begin with? Why not include it on the game card?

To get people used to checking for DLC so when they start announcing the pay stuff, you'll know to look for it.

To force more people to buy the game right away at launch instead of waiting a few months to buy it cheaper or used.  Unlike in North America were Nintendo can keep the price high for years, in Japan stores will lower the prices for Nintendo sometimes after just a few weeks if the sales aren't to hot, plus the used game industry is pretty huge in Japan as well.

Basically this will be Nintendo's way to try and maximize profits in Japan by making people either buy the games at full price for free DLC or buy it cheaper or used later on but will have to pay Nintendo for the DLC so Nintendo will still end up making around the same amount of money with each sale.

I will also add it alleviates the fear of accidentally buying something when your just looking.  This way it will encourage people to try to get the DLC.  Once someone now that they can do it and it isn't complicated there more apt to on the Pay DLC.

I'm wondering if they left space on the cart to store the DLC on there.

First hit is free.  Effective marketing tactic and addiction starter that's been used for generations.

Do you need the game to get the DLC? I have a tendency to download any free DLC on Xbox 360 and PlayStation 3, even if I doubt I will ever buy the game. LOL

Doubtful. They have SD cards for that now. It doesn't make sense to waste money on extra storage chips.