> If they're right, though, why should it matter how I use libmysql.so's APIs? Do socket() and connect() make libproprietary.so not a derivative work? Why? I can use an API over a socket too --- and if using an API makes my program a derivative work, then every proprietary program that talks to MySQL is in trouble.

As far as I know, the FSF takes the view that linking is a logical concept not a technical one, and so communicating via IPC is just as much of a problem as loading a program into your own addressable memory.

> This conclusion is absurd: therefore, our premises are wrong.

I don't think you've demonstrated that it's absurd. For instance, it could be that MySQL does not believe it is a problem, and does not intend for it to be a problem, and will never sue for it - but that MySQL is wrong as a matter of law, and one day the FSF will sue someone in court and win and the Oracle lawyers will realise they have new opportunities for financial gain. Personally, I think that reality is more like this - the FSF and Oracle have different ideas about what it means to release code under the GPL and so the freedoms you get from the FSF are different from the freedoms you get from Oracle, and it's unclear to me what will hold up in a court of law. I certainly don't think there's anything absurd about the notion that different agents have different intents and conflicting understandings. (Note that I take the notion of freedom to include the confidence that I won't be sued by a rational agent for doing something, regardless of whether I could plausibly win the case or not.)

> I know the industry behaves as if there were a difference, but legally, is there? Show me the case law.

I don't think it makes a difference whether the case law is there. The difference is made by whether you're willing to go to court over it. If there is a chance that you will win a case, and there is a chance that you will loose a case, and that if you lose the case you will have to spend the next six months on full time development just to get back where you were before hand, then you might say "even though my lawyers say there is an 80% chance that we will win, I would rather use this BSD alternative, because the risk of that 20% are existential".

So, fundamentally, this is a case of put your money where your mouth is. If you think the GPL does something different than what "industry" thinks it does, then make your business, make your millions, and dare someone to sue you. No one else has an obligation to do that just because you haven't seen the case law.

> I don't have permission to have it on my machine except by following the rules of the LabVIEW license. I don't need permission to have libmysql.so

Btw, here you have a false premises. You don't have permission to copy libmysql.so except by the terms of the licence. I think you've made a mistake. Let's go back. You said "I can already freely copy libmysql from system to system in either source or binary form. The GPL grants me permission to do that." But now you're claiming that the GPL's grant of permission is so absolute that you don't need the permission that it grants. In fact, the terms of the licence are limited, and the question is only to what extent they are limited.

In any case, there is one important consideration. And that is the intent of the FSF. If the terms of the GPL fail to have the legal consequence they intend, and they can modify the GPL to have the legal consequence they intended, then you can be sure they will. And if Oracle has a different intent, and likes the legal consequences that the GPL has, then they might continue to use the unchanged licence. But arguing about whether the GPL does to the FSF's code what the FSF wants the GPL to do is more about arguing about whether it is buggy, then arguing about the feature set. You are well advised to listen to the FSF's interpretation if you want to rely, indefinitely into the future, on an up-to-date version of the FSF's code. But the FSF's interpretation might not really be as important when it comes to Linux or MySQL or any of the other GPLed code bases out there.