A contributor is anyone in your GitHub organization who creates a pull request, potentially limited to members of a GitHub team. This does not include admins, reviewers, or people using the reporting features.
All public repositories, as well as any repository attached to an individual user as opposed to an organization, are included in the free plan.
No credit card is required to start a trial. Once a trial is started, anyone in the organization can enter a credit card to start a subscription. We use Stripe to store your card and process payments.
You can change plans or cancel at any time; no refunds.