Free 14-day trial is available to all first-time users who want to start analysing a private project. There are two ways of starting your trial, one that happens during sign-up (creating a premium account directly) and one that takes place after sign-up (switching from a free to a premium account).
During the sign-up process you choose a project you want to analyse. If you choose a public project from GitHub or Bitbucket your sign-up process is completed and your project will be analysed for free, forever. If you only end up analysing public projects you will never be asked for your credit card details, as simple as that.
However, if during the sign-up you choose a private project (which includes all self-hosted projects) then you're immediately asked for your credit card. This too will happen if you created an account with a public project and then later on attempted adding a private one.
All in all your free trial starts the moment you've added your credit card, even if you've been successfully using codebeat for your public projects for months! The trial lasts for 14 days during which you have full access to all premium functionalities of codebeat. You will only be charged at the end of the trial period so if you cancel beforehand (even on the 13th day) you will not have paid a single cent for your premium codebeat plan!
Note that the free trial is only available to first-time users of premium codebeat plan. If you've already been using codebeat and have canceled your subscription you are not eligible for the trial period. In that case the billing cycle starts immediately and your credit card is first charged the moment you enter it's details. Whether you've canceled during or after the trial period is irrelevant - even if you canceled your premium subscription after 1 day you can't get 13 days of trial period next time you want to go premium. If you feel strongly about it and you'll email us we can give you a coupon, though.