[ILUG] GPL and LGPL

[Paul Jakma]

On Fri, 22 Apr 2005, Robert Kiely wrote:

> But what about the libraries that are used... for example is it
> possible to use a proprietary libc with linux or does the GPL prevent
> this.

The GPL allows one to link to proprietary code, if that code is 
normally supplied with the system. See the last sentence of the 
second-last paragraph of section 3:

" 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."

If this were not made explicit, then GPL applications potentially 
could not run on systems with GPL incompatible libc's - which would 
have been a considerable problem back in the 80s and early 90s before 
there were any good 'Free' Unix systems available.

> As far as I understand the way that proprietary program run on
> linux is because all the libraries are LGPL. So I suppose what I'm
> really asking is about libraries that run on a kernel or interface
> directly with it... how does GPL software allow LGPL software to link
> with it ?

The Linux kernel licence contains a clarification that the syscall 
interface is considered to be the boundary of the GPL as it applies 
to the kernel. From <linux kernel>/COPYING:

"
   NOTE! This copyright does *not* cover user programs that use kernel
  services by normal system calls - this is merely considered normal use
  of the kernel, and does *not* fall under the heading of "derived work".
  Also note that the GPL below is copyrighted by the Free Software
  Foundation, but the instance of code that it refers to (the Linux
  kernel) is copyrighted by me and others who actually wrote it.

  Also note that the only valid version of the GPL as far as the kernel
  is concerned is _this_ particular version of the license (ie v2, not
  v2.2 or v3.x or whatever), unless explicitly otherwise stated.
"

glibc is LGPL, and hence (in torturous language) allows proprietary 
applications to link to it at runtime (static linking is more 
complicated apparently).

I've no idea whether or not LGPL libs may link to GPL libs. Ask a 
lawyer or google. :)

regards,
-- 
Paul Jakma	paul at clubi.ie	paul at jakma.org	Key ID: 64A2FF6A
Fortune:
Insults are effective only where emotion is present.
 		-- Spock, "Who Mourns for Adonais?"  stardate 3468.1