According to a Jalopnik interview with the stunt driver, Block learned of the site when a colleague was approached by its owners, Mad Media, who were hoping to sell advertising. Mad Media is the crew who produced a few of Block's early (and insanely popular) drifting videos, and the Ford Fiesta pilot says he was very surprised to find out that they owned the Gymkhana URL. When Block reached out to Josh Martelli of Mad Media, Block says he was basically told to go pound sand.
Martelli was also interviewed for the story, and he notes, "The automotive sport of gymkhana has been around since the 1900s... no one has the right to prevent the public from using the word gymkhana to report on, discuss, or promote the sport – especially on a website."
While he may be a little off-base on his history (in the 1900s, gymkhana was an equestrian sport), Martelli brings up an interesting point. The name and the driving discipline of gymkhana very much predates the Internet, but on the other hand, no 4-H video has ever garnered 160 million views on YouTube. Additionally, no single person is as strongly associated with the success of the sport as Block, and the relevance of Mad Media in this arena can largely be attributed to the vision of Block and his unique skill set.
For now, it looks like both sides are willing to drag out a costly lawsuit for the URL rights. Both will likely cite lofty causes for rallying around this flag, but at the end of the day, there is a decent amount of ad revenue to be made from the site, too.