They're under an affiliate rather than franchise model. I don't know enough about the differences to describe the differences other than to say that it seems to make Headquarters think they're unable to enforce standards once someone opens a gym.

I haven't done it myself, but to open an affiliate you need to:

(1) Write an essay.

(2) Pass their Level 1 certification class

(3) Have a website with a link to the Crossfit Journal

(4) Pay them $3000 (annually)

From: http://www.crossfit.com/how-to-affiliate

You need to pay HQ a sum ($3000, iirc) to license the name "CrossFit". They will only agree to that if you've completed their Level 1 certification. Once you've done that and paid up, you're on your own...