The Drupal trademark — that is, the word "Drupal" — is owned and controlled by Dries Buytaert, who cooperates with the Drupal Association and local non-profit associations to foster the use of the Drupal software. Revenues received from advertisements placed on this site are used to defray the substantial legal and administrative expenses associated with managing the Drupal trademark, which are the personal responsibility of Dries Buytaert as the registered trademark holder.
Trademark costs, fees, and expenses are indeed substantial, especially considering the varying requirements and licensing fees for various trademark organizations. At this point, trademark expenses far exceed the advertising revenue produced by this site. Trademarks must be affirmatively claimed to remain valid; this site helps to defray costs associated with remaining constantly vigilant against trademark infringement.