Depending on your plan type and repository's privacy, you will have a number of allotted credits available.
You can build both public and private repositories on the Performance plan. Open-source projects will consume credits, however, our engineering team is working to make OSS available on the Performance Plan.
You can build both public and private repositories on the Container plan, the first container is free. For open-source projects,
CircleCI provides Organizations 100,000 free credits per week ($2,880 annual value) to use for Linux open-source projects as long as repositories are public. Private repositories will have 2,500 credits/week available, which replenish every Sunday 12:00 UTC