A lot of people run sites and businesses with "Drupal" in the name. For the last 8 years, nobody's had to worry about licensing issues. Now things seem to be changing, and it's not really clear why.
A high-traffic website "drupalindepth.com" containing sponsored ads, qualifies for an automatic license when the profits generated from these ads (minus hosting costs and other obvious costs incurred for maintaining the website) are used to pay a full-time developer working on the new open source Drupal template engine.
And:
Example uses for which the license grant procedure must be followed:
* a commercial website hosted under domain name "commonusesofdrupal.com";
[Edit: IANAL]