From 0f3bc95c5160fe0492c1de0032dbf67405e9707c Mon Sep 17 00:00:00 2001 From: "Bradley M. Kuhn" Date: Thu, 20 Mar 2014 08:01:17 -0400 Subject: [PATCH] Rework pasted text into a coherent description of system library exception. This required writing a lot of additional text to make it work. I also added my cheeky rule of thumb. :) --- gpl-lgpl.tex | 61 ++++++++++++++++++++++++++++++++++------------------ 1 file changed, 40 insertions(+), 21 deletions(-) diff --git a/gpl-lgpl.tex b/gpl-lgpl.tex index 5b9a7ca..b63afd5 100644 --- a/gpl-lgpl.tex +++ b/gpl-lgpl.tex @@ -2463,30 +2463,49 @@ never be required to provide more than that. One always has the right to modify a source code work by deleting any part of it, and there can be no requirement that free software source code be a whole functioning program. -% FIXME: Standard Interface +\section{The System Library Exception} -% FIXME: System Libraries: it's in a different place and changed in later drafts +The previous section skipped over one part of the CCS definition, the +so-called system library exception. The ``System Libraries'' definition (and +the ``Standard Interface'' and ``Major Component'' definitions, which it +includes) are designed as part -The final paragraph of section 1 revises the exception to the source code -distribution requirement in GPLv2 that we have sometimes called the system -library exception. This exception has been read to prohibit certain -distribution arrangements that we consider reasonable and have not sought to -prevent, such as distribution of gcc linked with a non-free C library that is -included as part of a larger non-free system. This is not to say that such -non-free libraries are legitimate; rather, preventing free software from -linking with these libraries would hurt free software more than it would hurt -proprietary software. +to permit certain distribution arrangements that are considered reasonable by +copyleft advocates. The system library exception is designed to allow +copylefted software to link with these libraries when such linking would hurt +software freedom more than it would hurt proprietary software. -As revised, the exception has two parts. Part (a) rewords the GPLv2 -exception for clarity but also removes the words ``unless that -component itself accompanies the executable.'' By itself, (a) would -be too permissive, allowing distributors to evade their -responsibilities under the GPL. We have therefore added part (b) to -specify when a system library that is an adjunct of a major essential -operating system component, compiler, or interpreter does not trigger -the requirement to distribute source code. The more low-level the -functionality provided by the library, the more likely it is to be -qualified for this exception. +The system library exception has two parts. Part (a) rewords the GPLv2 +exception for clarity replaces GPLv2's words ``unless that component itself +accompanies the executable'' with ``which is not part of the Major +Component''. The goal here is to not require disclosure of source code of +certain libraries, such as necessary Microsoft Windows DLLs (which aren't +part of Windows' kernel but accompany it) that are required for functioning +of copylefted programs compiled for Windows. + +However, in isolation, (a) would be too permissive, as it would sometimes +allowing distributors to evade important GPL requirements. Part (b) reigns +in (a). Specifically, (b) specifies only a few functionalities that a the +system library may provide and still qualify for the exception. The goal is +to ensure system libraries are truly adjunct to a major essential operating +system component, compiler, or interpreter. The more low-level the +functionality provided by the library, the more likely it is to be qualified +for this exception. + +Admittedly, the system library exception is a frequently discussed topic of +obsessed GPL theorists. The amount that has been written on the system +library exception (both the GPLv2 and GPLv3 versions of it), if included +herein, could easily increase this section of the tutorial to a length +greater than all the others. + +Like any exception to the copyleft requirements of GPL, would-be GPL +violators frequently look to the system library exception as a potential +software freedom circumvention technique. When considering whether or not a +library qualifies for the system library exception, here is a pragmatic +thesis to consider, based on the combined decades of experience in GPL +interpretation of this tutorial's authors: the harder and more strained the +reader must study and read the system library exception, the more likely it +is that the library in question does not qualify for it. % FIXME: These don't belong here