GPL libraries and linking

[Erik Wikström]

Following the debate about whether Kororaa violated the GPL or not [1] 
by shipping the nVidia and ATI binary drivers I started thinking about 
the requirement that any code linked to GPLed code should be GPLed. The 
GPL-FAQ seems pretty clear, if code is linked with a GPLed library then 
the code must be GPLed too [2].

The question that I'm interested in is when a piece of code is counted 
as being linked with a specific instance of a library and when it is 
linked to an interface. To demonstrate my point I have a small example:

I decide that I want to make my own implementation of X and goes ahead 
and writes all the necessary parts, among them Xlib, and then licenses 
it all under GPL. Next I go and compile some X-applications, which would 
then be liked with my home-made GPL Xlib.

Obviously this can not be the way things work since it would then be 
possible to force every application that links to libc to be GPL, but 
still, the FAQ says that any program which uses a GPLed library have to 
be GPL too.

Can someone provide some insight in this?

1. http://kororaa.org/index.php?entry=entry060521-200059
2. http://www.gnu.org/licenses/gpl-faq.html#IfLibraryIsGPL

Erik Wikström
--
 "I have always wished for my computer to be as easy to use as my
 telephone; my wish has come true because I can no longer figure
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