And yet sqlite is the most distributed database code on the planet by an order of magnitude.

No one does any due diligence on software. It's a free for all.

It’s distributed in MacOS, Chrome, Firefox, etc. I think these companies do due diligence.

Edge case. In every company on the surface of this continent people import libraries and run software with no idea what is under the hood and whether they are compliant with all the applicable license agreements. Some clumsy attempts are made for major systems in some companies, but again, edge cases.

What part of Public Domain do these legal departments not understand?

It's not that they don't understand; it's that it causes more work for the lawyers, because someone has to review the license if it's not one of the standard boilerplate acceptable licenses.

I once had to go to lawyers to get a license approved on a lib that went something along the lines of "this work is in the public domain; do whatever the fuck you want with it, just don't come crawling to me for help". I'm paraphrasing from ~20-year-old memories here, but I do distinctly remember the profanity. It elicited a chuckle from the lawyer and something along the lines of "I wish all of these were this simple".

JSLint had a standard open source license with an addition that said “The Software should be used for Good, not Evil.”

IBM wanted to use it but their lawyers balked at the added restriction. They wrote to the author to see if it could be removed. The author wrote back with, “I give permission for IBM, its customers, partners, and minions, to use JSLint for evil.”

If you're doing this sort of license analysis, try a license detector I built. It tries to guess which license was used and diff any changes. Lots of licenses are small changes from others, so it usually makes multiple guesses.

https://alexsci.com/which-license/

Sounds like https://en.wikipedia.org/wiki/WTFPL

"DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE"

They understand quite well that it's not really something you can just neatly place a piece of work into. Something which is 'public domain' but the copyright has not actually expired on is higher risk to use than something with an explicit open source license.

The US isn't the only jurisdiction, and public domain isn't a concept in all jurisdictions.

But in this jurisdictions without a concept of public domain, who is going to come after you for using software without an explicit license?

That’s not enough which is why this page exists:

https://www.sqlite.org/purchase/license

I mean, like Germany?

And legal departments don't really like the "but, like, what's the chance they actually use us?" argument.

Software without an explicit license has all rights reserved, so presumably the author, if they ever regretted releasing their rights in the US.