I suspect there is some incoherent thinking about the BSD license. If you are a BSD advocate, consider this:
Someone takes a BSD project and bases a proprietary program on it. Is that person doing something wrong? Well, no, you say, because that's the whole point of the BSD license. It's also fine to keep rolling in new versions of the BSD project.
Now suppose someone takes a BSD project and relicenses it under the GPL, announces it on the internet, gets it into all the Linux distributions, and starts soliciting contributions of new GPL-only features while also rolling in new versions of the BSD project as they become available. Is that person doing something wrong?
I suspect that a calm, "No, that's also great. That's why we made it available under BSD." would not necessarily be the response.
This is how I think about BSD vs. GPL issue (of course, it's a contrived example and numbers are not accurate):
You have created X (say, redis). 5000 individuals and companies need it right away and want to use it momentarily.
If it's in public domain, all of them will use it, then make separate forks, and maintain them (individually, or in groups).
If it's a commercial product (say, $20.000), you might get 10-20 customers. They won't contribute back code, but will give you loads of money so you can hire more people. It's great business, but a couple of teenagers can't hack away with it because it's just too expensive.
If it's GPL, 500 companies (10%) will use it. Because if they use it, they have to re-licence their code as GPL also, which is unacceptable in many cases. They all contribute back their modifications though, which is great.
If it's BSD, everybody (5000 people) can and will use it (as it doesn't require you to contribute back your modifications, and you can have a private fork). So, we have 5000 companies using X. How many of them are contributing back? If it's more than 10%, then it's a win. If it's less, it's a loss (compared to GPL).
In other words, if you GPL you code, your pool of potential contributes has shrunken substantially.
---
So, the question is this: which is bigger? the percentage of companies that can use a GPL-licenced software, or the percentage of companies that are using BSD-licenced software and are contributing back their changes. I think in a lot of cases, the second one is bigger.
If it's in public domain, all of them will use it, then make separate forks, and maintain them (individually, or in groups).
SQLite is almost exactly analogous to what you described (database, public domain).
AFAIK, there is no widely-used SQLite fork.
IOW, the situation you describe with every company "maintaining their own fork" literally did not happen to the software that's the closest case study in real life to what you describe.
But also any GPL project can poach from a BSD project, but not the converse, so BSD contributions are (technically) a strict subset of GPL contributions.
I don't understand. Why would the developer who wants his code used "anyway you see fit" suddenly care how you re-licensed it? You have used it in a way you see fit. The original BSD license didn't evaporate. This situation looks no different to me than a company taking a BSD-licensed project and putting it inside their proprietary systems.
If his downstream users are savvy enough to know to use this "forked" project, they're savvy enough to search for the original author and discover that they can get the same code under a more permissive license.
Say you release code X under a BSD license. Someone incorporates a neat, but tricky to re-implement, feature and release the code under GPL. Everyone wants that new feature but, if they do, they either have to reimplement it without looking at the GPL source code, or they have to use the GPL license from now on (or, third choice, live without that feature). I used to release my code under a GPL license but found too many restrictions. The worst offenders were tutorials written where the code was GPL. Tutorials that aim to free you by giving you new knowledge should not tie your hands and force you to adopt a license if you want to use that knowledge.
Has something like that ever happened? I always hear this sort of argument against BSD— "But what if a company takes your project, strips it of all references to the original, and sells it as closed-source proprietary?!"— but I've never heard of it actually being successful. The same with your example. Has that happened before, or is this just a case of premature optimization?
The reason the GPL happened in the first place was because this happened to Stallman with the original version of Emacs he wrote with his friends. He started personally reimplementing every feature they added under a forcibly-free codebase to guarantee this would never happen to him again. (Additionally, this happened to me; I got totally shafted by assuming people would play fair with a BSD license, and the result was a closed-source commercial competitor with investment funding and a marketing department running rings around me. They really were reliant on my codebase, so temporarily closing source and moving to GPL undid some of the damage, but the consequences persist to today.)
Never heard about it happening to a BSD licensed project, but it has certainly happened to GPL licensed projects. Some years ago there was a company who rebranded a GPL'ed CD ripping program, removed all author credits and sold it without source. The authors eventually found out through disassembly.
Someone takes a BSD project and bases a proprietary program on it. Is that person doing something wrong? Well, no, you say, because that's the whole point of the BSD license. It's also fine to keep rolling in new versions of the BSD project.
Now suppose someone takes a BSD project and relicenses it under the GPL, announces it on the internet, gets it into all the Linux distributions, and starts soliciting contributions of new GPL-only features while also rolling in new versions of the BSD project as they become available. Is that person doing something wrong?
I suspect that a calm, "No, that's also great. That's why we made it available under BSD." would not necessarily be the response.