"If the project you’re backing is successfully funded, your card will be charged when the project reaches its funding deadline. If the project does not reach its funding goal, your card is never charged. That's why we call them pledges." This is from the Kickstarter FAQ page (http://www.kickstarter.com/help/faq/backer+questions#BackAProj)
Don't see the answer to your question? Ask the project creator directly.