According to their website the Chatterbox Challenge is:
...is an annual contest for chatbots. It is unique in the fact that minimal restrictions are placed on the type of technology used in the creation of the bot. The competition will begin in early March and finishes shortly thereafter. Botmasters from across the globe submit their chatbots for evaluation and competition. Every entered chat bot is asked a series of questions and scored on its responses by a set of independent judges. The top eight bots move to a final round where an additional series of questions is posed to the finalists. The winner is selected by the judges as the chatbot who has scored the highest from among the finalists. A number of the chatbots who have entered the competition in the past have become the foundation for commercial technologies.
A few Verbot knowledge bases were entered into the competition and won. In 2005 the Verbot "Julia" won 3rd Place for Best Interface:
In 2007 the Verbot "Athena" took home 1st Place for Best New Entry: