Some thoughts on MySQL and Oracle [LWN.net]

Some thoughts on MySQL and Oracle

Posted Dec 15, 2009 20:05 UTC (Tue) by rahulsundaram (subscriber, #21946)
In reply to: Some thoughts on MySQL and Oracle by rahulsundaram
Parent article: Some thoughts on MySQL and Oracle

Ah, I meant LGPLv3 and GPLv2.

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Some thoughts on MySQL and Oracle

Posted Dec 17, 2009 17:39 UTC (Thu) by RobSeace (subscriber, #4435) [Link] (5 responses)

So, wait... LGPLv3 allows a totally closed-source proprietary app to link against it, but yet somehow DOESN'T allow a GPLv2-only app to link against it?? How does THAT work, exactly?!

Some thoughts on MySQL and Oracle

Posted Dec 17, 2009 17:46 UTC (Thu) by ballombe (subscriber, #9523) [Link] (4 responses)

You frame it the wrong way. LGPLv3 certainly allow GPLv2 apps to link against it. However, GPLv2 does not allow to link against LGPLv3 libraries, because the LGPLv3 contains additional restriction that are not in GPLv2.

Some thoughts on MySQL and Oracle

Posted Dec 17, 2009 18:42 UTC (Thu) by RobSeace (subscriber, #4435) [Link] (3 responses)

Wait, if that were the case, then GPL2 apps would be unable to link against proprietary libcs and such on other systems, which is clearly allowed... You just aren't allowed to distribute the two together as a unified whole... So, what may be forbidden is distributing a combination of an LGPL3 library along with a GPL2-only app that links to it... I can see that as possibly problematic, but how could it be problematic to write and release a stand-alone GPL2-only app which happens to link against an LGPL3 library? If one can link against closed-source system libs without poluting the GPL2 code, surely LGPL3 is no worse/dirty??

Some thoughts on MySQL and Oracle

Posted Dec 17, 2009 18:58 UTC (Thu) by mjg59 (subscriber, #23239) [Link] (2 responses)

The FSF's stated position is that you can only link against closed libraries because of this
section of the gpl:

"However, as a special exception, the source code distributed need not include anything that is
normally distributed (in either source or binary form) with the major components (compiler,
kernel, and so on) of the operating system on which the executable runs, unless that component
itself accompanies the executable."

The FSF's belief is that without this clause, a GPLed application can only be distributed if the
libraries it links against are also available under terms compatible with the GPL. The
GPLv2/LGPLv3 incompatibility follows from this - LGPLv2 also includes restrictions that are
incompatible with the GPLv2, but LGPLv2 explicitly allows you to use the code under GPLv2
instead. LGPLv3 only allows you to fall back to GPLv3, which itself is incompatible with GPLv2.

Now, the fact that companies like Sun and Apple distribute GPLed code linked against their non-
GPL compatible system libraries as part of their default install (and so would seem to trip over
the "unless" component of the above) indicates that they appear to have a different belief about
what a derivative work is. I don't know of any cases which have actually tested this, and I
suspect it's in the FSF's interests to leave it as a grey area for the moment.

Some thoughts on MySQL and Oracle

Posted Dec 17, 2009 20:33 UTC (Thu) by RobSeace (subscriber, #4435) [Link] (1 responses)

But, given the hypothetical situation of a distro shipping some LGPL3 library as standard, then why couldn't a GPL2 app (not distributed as part of the distro) make use of that same exception you quote in order to use the LGPL3 library without changing its own license? (And, following from that, one could easily produce a distro that distributes the library as standard, if one chose to, which means that effectively ANY LGPL3 library fits into this exception... And, of course, you couldn't stop end-users from using your app on a different distro that didn't ship the lib as stock, and what they do with combining your app with non-compliant libs on their own systems is out of your hands and out of the scope of the GPL...)

Some thoughts on MySQL and Oracle

Posted Dec 17, 2009 21:53 UTC (Thu) by mjg59 (subscriber, #23239) [Link]

You can certainly do that, but the majority of Linux distributions consider themselves to distribute
all their packages alongside all their other packages - that is, you effectively rule yourself out of
being included by default in any mainstream Linux distribution. That doesn't matter to some people,
but it does to others.