Thoughts
I hate the OSI's response to public domain. It's literally just vague fear-mongering.
They provide no examples. They're just 'this is confusing. I'm not a lawyer and you're not either. It's impossible to know what "public domain" means. Anyone who wants to use public domain software should talk to a lawyer. You might not actually be able to use it. If you're still confused, read 3 months of mailing list archives from 2012. You think that's unreasonable? Then trust us, just use an OSI-open-source-approved license.'
They do argue you shouldn't CC0, since a) CC0 explicitly disclaims that the author may hold a patent on the content and b) CC0 doesn't include a disclaimer of warranty. (Which is a result of CC0 being intended for media, not software.) But like, there's no mention of the Unlicense or Zlib or BS0 or similar.
Sources! Because I apparently I hold myself to a higher standard that the OSI ("if the thought of reading all those conversations is daunting, please take that as more evidence that it's just better to use an approved Open Source License if you can!").
=> https://cr.yp.to/publicdomain.html One of the prominent anti-Public domain lawyers retracts his statements when it's pointed out that he is contradicting the Ninth Circuit.
=> https://unlicense.org The Unlicense. The Unlicense is verbose, and claims that its verbosity is necessary to safely public-domain software. Which doesn't exactly help. But it does address all of the concerns of the OSI and is OSI approved. The list of sources at the bottom is also pretty good.
There are other OSI approved licenses that are also effectively public domain: 0-clause BSD, Zlib, etc.
=> http://harmful.cat-v.org/economics/intellectual_property/ Libertarian Propaganda (please read) (Also see links at the bottom of this page.)
=> https://opensource.org/faq#public-domain The OSI's 1000 words that say nothing in their FAQ.
=> https://opensource.org/node/878 Another 1000 words on the OSI's website that repeat the same bland talking points. "It’s probably safer to use a license like MIT instead." (Just in case I haven't made my point well: This quote is dumb. If I want to public-domain my code, saying "just don't" isn't helpful.)
(This post was inspired by the Gemini user who claimed that most people who don't support the OSI are trying to profit off of open source.)