Infectious licensing: helpful or hurtful?

This is a non issue. It is about freedom of choice.

It is the copyright holders choice to license out code under GPL or LGPL. What GPL and LGPL do for the copyright holder is to require that any any improvements to code licensed out under GPL or LGPL is made available to the original copyright holder and others who wish to improve it. This gives protection to the author, by preventing someone else taking the author's work improving it and then using the improved work to put the author out of business. With GPL and LGPL, any improvemenmts made by others will be available to you also. BSD is problematic in this respect and so is not as popular among copyright holders.

GPL and LGPL allows copyright holders to release software under multiple licenses. GPL or LGPL for those who want it under GPL or LGPL, and under propeietary terms under those who want it proprietary.

If you need to license software under another terms other than those offered by the copyright holder of the code concerned then you need to reach an agreement with the copyright holder to license it to you under these other terms. Many copyright holders make money by dual licensing - eg Trolltech with the QT libraries used in the KDE desktop, and MySQL. It is down to the copyright holder. You can't force MySQL to license under the BSD license if they don't want to any more than you can force Microsoft to license Windows or MS Office under BSD license.

As for the title of the piece, it is never necessary to license GPL code for interoperability. The method is not protected by the copyright. If you want, you can look through the code to find the method, and write your own code from scratch using the same method and license it under a proprietary license if you want. You can talk to the copyright holder and ask for a license as you would with proprietary code, but as with proprietary code, you can't copy it without a valid license.

You do have a major point though. The problem for interoperability is not GPL, LGPL or copyright, but patents. These protect the method, and therefore can prevent interoperability. What you/Vetter should be saying is that interopeability should trump parents.

"Does this mean MySQL (and Alfresco, and Sugar, and...) is not open source? Of course not. No less so than Linux. What it means is that such companies recognize, like Vetter, that the road to open source is not through force/compulsion but rather through interoperability."

I would say quite the reverse. As the copyright holders, MySQL and people using similar strategies can dual-license. For commercial purposes, that gives them the best of both worlds. Having the programs out under an open source license creates a general universe of users and a general realization that there is something there that would be worth embedding. But if it were not GPL, they wouldn't pay MySQL for its use--the compulsion of the GPL is what MySQL depends on to make people who would use the code for closed purposes to come to MySQL and pay rather than simply appropriating the code. Arguably it's also what ensures that the original, open source version remains the primary one.