On 23/07/10 10:57, Andrew Fitzgerald wrote:
Saw an article mentioned on Slashdot about Wordpress themes and plugins being required to be disributed under the GPL because they are derivative of Wordpress. Is this also true for Mediawiki extensions and skins? It seems like the arguements for why Wordpress themes and plugins also apply to MW.
Article: http://markjaquith.wordpress.com/2010/07/17/why-wordpress-themes-are-derivat...
In my opinion, MediaWiki extensions are not derivative works unless they copy substantial portions of core MediaWiki code. If an extension merely uses the interface MediaWiki presents, then it is not a derivative work, and the authors of MediaWiki have no right to place conditions on its distribution.
To adopt an interpretation of copyright law which claims that merely calling code constitutes a copyright violation of the code which is called would, in my opinion, be a terrible stance for a free software advocate to take. For instance, it would bring into question the legality of all open source code which runs on top of the Windows native API, such as 7-zip, not to mention Wine and Mono.
The two legal theories which would allow the use of an interface are:
* A function name or class name are not creative enough or substantial enough to be eligible for copyright.
* A function name or class name is a small excerpt from a work, used for the purposes of precisely referring to a larger part of the work. Such reproduction of an excerpt is fair use. This is the same legal theory which allows us to reproduce things like chapter titles and character names in Wikipedia articles about copyright novels.
Aryeh Gregor wrote:
The FSF's position on the issue is that plugins, extensions, and things like that, which link to/call code from a GPL program, must themselves be licensed GPL-compatibly:
When I agree to the GPL, and when I consent to allow my work to be distributed under the GPL, I'm agreeing to the actual text of the license. I'm not agreeing to every piece of nonsense that has ever come out of Eben Moglen's mouth. I'm not even agreeing to the "How to Apply These Terms to Your New Programs" section, which is explicitly outside of the license itself.
There is no way the GPL can restrict code which is not licensed under the GPL, and is not derivative (in the sense of copyright law) of any GPL work.
In GPL version 3:
* Section 4 explicitly permits verbatim copying of GPL-licensed code, and does not place any restrictions as to linking or calling non-GPL code. Section 4 gives the author of a non-GPL extension permission to copy the MediaWiki core. It also allows GPL extensions to non-GPL code to be copied.
* Section 5 applies only to derivative works, and as I said, it would be a terrible thing for the free software movement if it were to attempt to apply this term to code which merely calls a copyrighted interface.
If section 5 did apply to function calls, then every GPL program would have to display prominent notices crediting the copyright holders of every GPL library which it called, due to sections 5(a) and 5(d).
* Section 6 applies only to the distribution of non-source forms of the work. Because MediaWiki and its extensions are only distributed in source form, this section does not apply to it. But even for programs written in C, section 6 does not restrict dynamic linking from GPL programs to non-GPL programs, or vice versa.
Only the "how to apply these terms" section mentions linking:
"The GNU General Public License does not permit incorporating your program into proprietary programs. If your program is a subroutine library, you may consider it more useful to permit linking proprietary applications with the library. If this is what you want to do, use the GNU Lesser General Public License instead of this License."
But as I said, I never agreed to that and I don't intend to start now. It comes after the words "END OF TERMS AND CONDITIONS".
The GPL does not restrict dynamic linking of non-GPL code to GPL code. If it did, it could only be implemented by restricting distribution of the GPL part, because the licensor has no right to place restrictions on the copying of works which are not derivatives.
-- Tim Starling