Get Open Collective data.
Open Collective API is a free Social API that requires no API key, is served over HTTPS and has unconfirmed CORS support.
Details from docs.opencollective.com.

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The Open Collective API is provided by Old Open Collective Docs (docs.opencollective.com).
Yes. The Open Collective API is listed in the Social category of the public-apis directory, which only includes APIs that are free or have a free tier. Check its documentation for rate limits and paid plans.
No. The Open Collective API requires no authentication, so you can start making requests without signing up.
CORS support for the Open Collective API is unknown. Test a request from the browser, and fall back to a server-side call if it is blocked.
Yes. The Open Collective API is served over HTTPS, so it's safe to use in production.