Stallman was hesitant but in favour of this. He called it selling exceptions. His reasoning is that selling exceptions merely permits someone else to create non-free software, but that weak free licenses like the MIT license already allows this, therefore, selling GPL exceptions wasn't worse than weak licenses, in his view.
bkuhn has had more first-hand experience with it. It's been disastrous. The way exceptions are sold are by scaring copyleft users with frivolous copyleft violations and offering them no recourse to correct the violation except by buying a non-free license. Oracle and Mongo are the most famous examples of vendors who bully their users with threats of copyleft violation, telling them the only way to correct the violation is by paying.
I read the whole thing waiting to get to an example of what a "frivolous" violation is. I probably agree with him or her but it does hinge on that and it's an important detail to leave out.
Best short summary of Stallman's published position I've seen. Nice.
I also have first-hand experience with selling exceptions. My experience has differed markedly from Bradley's. Lots of small companies sell exceptions without any aggressive, professional, commission-driven sales team. Many publish helpful guides and FAQs on their licensing situations that clear up confusion about the (A)GPLs. Some have chosen new or different public licenses, in much plainer language, to avoid that confusion in the first place.
For what it's worth, I remember reading Bradley's secondhand report of shakedowns by MongoDB. I've never worked directly with MongoDB, either, but I was surprised. What I've heard from MongoDB employees is very different: they spent a lot of time sending out "comfort letters" clarifying that people could use AGPL Mongo in their applications without releasing the whole shebang.
I don't think Mongo sends such letters to competing cloud providers. When it comes to proprietary cloud providers, I thought the point of AGPL was to demand cloud users share alike or leave AGPL code alone.
I think Bradley and I would probably agree that big companies have given dual licensing a bad name. But we might agree they've often done the same for permissive licenses, too. I don't think little companies, especially little companies not Hell bent on becoming behemoths or getting acquired by them, deserve the bad rap.
From a business point of view, small companies are precisely where dual licensing matters. Oracle-scale companies can well afford to develop and manage differentiated open/community and enhanced/enterprise projects. If they're selling exceptions for the whole codebase instead, it's likely either dead-end code they don't want to invest in, or they're up to something else, leveraging their other BigCo advantages.
https://www.fsf.org/blogs/rms/selling-exceptions
bkuhn has had more first-hand experience with it. It's been disastrous. The way exceptions are sold are by scaring copyleft users with frivolous copyleft violations and offering them no recourse to correct the violation except by buying a non-free license. Oracle and Mongo are the most famous examples of vendors who bully their users with threats of copyleft violation, telling them the only way to correct the violation is by paying.
https://sfconservancy.org/blog/2020/jan/06/copyleft-equality...