Starting February 2014, no more credit card is needed to start your trial period, on all paid plans (Bronze, Silver, Gold).
If you are happy with our service, just provide your credit card information before the end of the trial period. The billing will start automatically at the end of the 30 days.
Not happy? We're sorry we didn't convince you! Don't worry, your account will be downgraded to a Free one, and you will still be able to monitor open-source projects.