I wrote that post. I generally advise developers, and believe most of my US colleagues also advise developers, to treat past releases under MIT and BSD terms a

I wrote that post. I generally advise developers, and believe most of my US colleagues also advise developers, to treat past releases under MIT and BSD terms as irrevocable, even though they don't explicitly say they are. But that conclusion comes as much from practicalities as legalities. If the MIT license lets people make and share copies willy-nilly, online and off, how do you go about notifying every potential recipient that you've taken that license back? Even if you send a notice to just one user you want to block, who wants to see that on the Internet within hours? Who wants to be the company potentially arguing in court to undermine the reliability of MIT license grants generally? On the legal side, sketching very roughly: The general rule seems to be that non-exclusive licenses without terms remain revocable by default. But in what circumstances won't a court find a contract or quasi-contract, applying those rules instead? So much better to get ahead of all this head scratching by saying in the terms that those giving can't take them back. Alas, literally nobody's got commit bit on what we call "MIT", "BSD", &c. anymore. But we made very sure to do it the Blue Oak Model License: https://blueoakcouncil.org/license/1.0.0#reliability https://blueoakcouncil.org/license/1.0.0#reliability Other, more recent forms, notably Apache 2.0, say it, as well. If you're reading this and thinking about a particular bit of software, don't rely on what I've written here. Talk through it with a lawyer who's up to speed on the latest, will ask you for specifics, and will stand professionally responsible for their guidance. I won't.