The Creative Commons organization explicitly marks in their FAQ that
`CC0` is fine for software.  Besides, many software projects are
released under it and it is considered `GPL` compatible.

Reviewed-on: #704
Reviewed-by: Gusted <gusted@noreply.codeberg.org>
Co-authored-by: Clara Engler <cve@cve.cx>
Co-committed-by: Clara Engler <cve@cve.cx>