UPDATE: This works great, I had my friend buy and download the maps on his 360 with my gamertag, then I downloaded them on my 360, and we're both online playing right now. There are some drawbacks, but why pay $15 when you can pay $7.50?

First of all, I know for a fact that this works with DLC for some other games.

The plan:

1) Find a friend, someone that you trust. Don't do this with a random person online if you plan to share account info.

2) Person 1, who intends to purchase the DLC with their own account, moves their account to Person 2's 360, either via a memory card or online migration of your gamertag.

3) Purchase and download the maps on Person 2's 360, and try them out.

4) Person 1 moves their gamertag back to their own 360, goes to "Account Management" and re-downloads the maps.

5) As long as Person 1 does not re-authorize Xbox Live purchases back to their 360, the DLC should be active on both.

I have done this before with Trials HD. I am a college student and when I go home to visit my family I bring a memory card to play on my brother's 360. I downloaded the Trials HD Big Pack with my profile on my brother's 360, and when I went back to school I downloaded it on mine as well, and both of us can play it just fine, and even at the same time.

As I understand it, DLC is not only tied to your gamertag, but to the console you purchased it on. You can't buy the maps on your own console and then go around to all of your friends' consoles and download it for them too, because your gamertag must be signed in on to play content if the console isn't where the content was originally purchased. However, any gamertags that are on the console of original purchase should be able to play the content even if the purchaser's account isn't signed in.

I'm pretty sure this will work, but I don't want to spend the $15 in case it doesn't. Is someone with a friend nearby willing to try this out and tell me if it works?