-- Dave
From: [EMAIL PROTECTED] (Linus Torvalds) Date: 1995/12/17 Message-ID: <[EMAIL PROTECTED]> Sender: [EMAIL PROTECTED] References: <[EMAIL PROTECTED]> Content-Type: text/plain; charset=ISO-8859-1 Organization: University of Helsinki Mime-Version: 1.0 Newsgroups: gnu.misc.discuss
In article <[EMAIL PROTECTED]> , Paco Moya <[EMAIL PROTECTED]> wrote: > Some weeks ago I posted an article on a probable violation of the GPL. > It was about a device driver for a frame grabber which could be > dynamicaly linked with Linux or statically linked with it. > > Some people, namely Linus himself, stated that it was fair use of > the GPL'd code (the kernel) because no line of code was apparently > used and the driver was independent enough. > > I'm not a lawyer but I cannot accept this interpretation of code reuse. > A device driver is not in any way independent of the kernel with which > it interacts. I'm not talking about interface copyright or patents but > about logical dependance.
Note that there is no such thing as "dynamically link into the kernel" in linux. Instead there are "loadable modules".
Now the above may strike some people as nit-picking, but there is one rather important thing about loadable modules: they can _not_ link themselves against any random kernel routine. And the routines they _can_ link against are routines that I consider to be "logically independent" of the kernel implementation.
Essentially, the kernel module interface is a "library" interface to the kernel, and kernel modules are considered to be under the GNU _Library_ license. In fact, due to the way kernel modules work, you automatically do it according to the LGPL so this isn't explicitly stated anywhere, but that's the way you should think about this.
Another way to look at this - using the legal rather than the moral viewpoint - is to just see module loading as "use" of the kernel, rather than as linking against it. I prefer to explain the rationale behind it using the _moral_ reason to do it, though.
The reason the kernel is exposed in such a LGPL'd way when using modules is simply that there are a lot of kernel device drivers for unix available, and they were not all written under linux. If somebody wants to port his SVR4 driver to linux but doesn't want to GPL it, I feel that he should have the right to do that, using modules. After all, the driver wasn't actually derived from linux itself: it's a real driver in its own right, so I don't feel that I have the moral right to force him to switch copyrights.
Now, the above said, I _much_ _much_ prefer GPL'd drivers, even if they are available only as modules. Especially if they were actually originally written _for_ linux, I consider it a bit dodgy to not use the GPL (they can potentially be considered derived works even if you don't actually link them into the kernel per se). But I do not want to force it on people that arguably are _not_ doing derived work (it would be rather preposterous to call the Andrew FileSystem a "derived work" of linux, for example, so I think it's perfectly ok to have a AFS module, for example).
For several reasons a linux module also doesn't always make much sense unless it comes with sources - if some commercial company thinks that linux is important enough that they want to do a commercial module for linux, they may also recognize that a binary module doesn't work for most linux users who use experimental kernels, for example.
Final note: the linux interpretation is not a "normal" case. I wouldn't use it as a guide-line to anything else, especially not in user mode.
Linus
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