Sorry - if I purchase a copy of your product and it is GPL licensed I
can ask for the source, expect to receive it, and then start selling
it myself with near zero development overhead. I can also purchase it
once and give it to all my friends, source and all. I can basically
wipe out your business if I've a mind to. It'd all be legal. It might
be unethical as all hell. But it'd be legal.
If I am the original author the license does not apply to me. I do not
have to give anyone squat. Basic copyright law applies. The GPL is based
on copyright law and therefore the license doesn't control what the
original author can do.
If you actually take lines of source from a GPL licensed project and
use that source in the source for your product then you have created a
derivative product and therefor must license it as GPL. If, however,
your source code only call GPL'ed libraries (said libraries are
LGPL'ed)
and/or use make use of external GPL tools and apps in your source
you do
not have to release your stuff under the GPL.
If you take a substantial portion of the source of a GPL licensed
code base such that copyright law comes into play then you must make
your code also available under the same license if you redistribute
the program. If you only take one line from a large code base then
it's unlikely to be a substantial part of that code and copyright
won't come into play. Usually libraries are under the LGPL but they
can be under the GPL and likewise non-libraries can be LGPL. There
are different issues with using each license. As with any license you
should read it and understand it before agreeing to it. In the case
of software using the program or code is agreement.
Have you looked at the KDE license chain lately? Have you looked at
licensing device drivers for Linux lately. Even if you build and
release "glue" code and try to include a proprietary module people
are claiming that the glue code and your proprietary module are
all one project so the proprietary module is now GPLed. They may
still be quibbling over a proprietary driver developed specifically
for one OS and later on a glue module produced for Linux. Many are
saying that if it's the same company doing both then it's "obvious"
that the glue module was all part of that one project hence the
contamination is real.
I don't care for KDE so I can't say that I've looked at it. Glue code
can be a sticky issue depending on how it works but in most cases there
are clearly defined issues of what does constitute a derived work and
what doesn't. Usually it's okay to interface to other programs but not
to compile their code into your code. Maybe if they are having an issue
they should look at how other projects have solved this issue. This is
not a GPL specific problem by any means. Anytime you have two pieces of
code under different licenses being integrated closely this happens
unless the two licenses have been made to be compatible. This is one
reason for the resent push to eliminate as many of the open source
licenses as possible. The BSD, LGPL, and GPL cover most of the important
differences projects might want to take advantage of. Now we need to
just eliminate proprietary licenses and all will be fixed. ;)
For myself, I avoid using proprietary code whenever possible in both my
personal use and business use. If a program isn't open source I don't
want it. If a device uses a non-open driver then again I tend to frown
on it although it's harder to avoid those as so many hardware companies
still have their head up their ass in their imagination that open
drivers are going to help their competition more than it helps themselves.
