Fedora to disallow CC0-licensed code

Right, but this doesn't make any sense because of the different nature of copyright and patents. If you have written some code (and not plagiarized) then you are the copyright owner and a licence from you is sufficient. But any unrelated person, who might never have seen the code in question, can assert patent claims. Perhaps the very broad, poor quality software patents we worried about a decade ago have been neutered by court decisions, but still in principle the code's author and the holders of software patents need have no relationship. So I don't see why Fedora is insisting on a patent licence or waiver from the original author. If they don't hold any software patents and haven't even applied for one, then there is nothing to grant anyhow. And even if they did add a clause to the licence, that would do nothing to lower the risk of patent lawsuits in practice, since that risk comes from third parties.