Our WebFont license explains that “You may use one Licensed WebFont on one domain name (URL) only.” The spirit of this restriction is to the separate nature and control of the content.
For example, “starwars.disney.com” and “marvel.disney.com” would require two separate WebFont licenses, since they represent two entirely different products with entirely unrelated content, under the control of different people/parties–even though the parent company is the same.
If you, as the licensee, are in control of all of the content on several subdomains, and they are not actually separate URL’s with different content controlled by separate parties, you may buy one license to cover them all.
Just be sure to total all of the monthly page views of all of the subdomains in question, and buy the appropriate level of coverage.
Please contact us if you need further clarification, we’re always happy to help make licensing easier to understand.