Join Cloud.typography and get your first five webfont packages FREE.
  Choose from among H&FJ’s complete library of type families, known for
  their plentiful styles and rich typographic features, each carefully engineered
  to be fully functional in the browser.

and

  Already purchased H&FJ fonts? Log in and start your subscription, and you’ll
  find all your fonts available to use with Cloud.typography at no additional cost.
  Buy fonts for your computer, and they’ll instantly appear in your
  Cloud.typography webfont library, too.

…seems to indicate that you pay for a base subscription (based on pageviews) and they handle hosting/serving all the fonts that you've purchased. It's not "all-you-can-eat".