Licensed under CC-0, making it technically Public Domain, allowing you and anyone else to freely copy and use it without restrictions.
It’d be more correct to say “Released into the public domain using the CC0”, because the CC0 isn’t a license. It’s a public domain dedication that falls back to a license and promise not to sue in jurisdictions like Germany where you’re not allowed to prematurely put things into the public domain.
(And boy, is Germany an intestering case. Give this a read for an overview of what the CC0 has to go through to say “Yes, I really do know what I’m doing when I want to waive the protections you’ve written into law for me.”)