CC0 is awful for code. I didn’t understand why until reading this https://lists.opensource.org/pipermail/license-review_lists.opensource.org/2012-February/001431.html (you can click the thread button to see the full thread as well).

• Many licenses like GPL and Apache explicitly say patent rights are waived and the patent holder can’t sue the user.
• Many licenses like MIT are believed to implicitly do this because of the language used.
• CC0 specifically states that it does not give you patent usage.

https://creativecommons.org/publicdomain/zero/1.0/legalcode.en#limitations

No trademark or patent rights held by Affirmer are waived, abandoned, surrendered, licensed or otherwise affected by this document.

The only license/declaration approved by both the FSF and OSI for putting something into the public domain while having a permissive fallback license (for jurisdictions without public domain) is the Unlicense. If you know of others please let me know.