GPL Infectiousness

[Michelle Lowman]

On Mon, 2002-09-30 at 20:40, der.hans wrote:
> Am 29. Sep, 2002 schwätzte Robert Bushman so:
> 
> > I missed Michelle's lecture, but the GPL is
> > intended to provide Free Software developers
> > with an advantage that is unavailable to
> > proprietary software developers:
> >
> > "Proprietary software developers have the advantage of money; free
> > software developers need to make advantages for each other. Using the
> > ordinary GPL for a library gives free software developers an advantage
> > over proprietary developers: a library that they can use, while
> > proprietary developers cannot use it.
> 
> It doesn't give us an advantage. They can use it as well, but under the
> terms of the GPL. I can buy code from Rational Software to use in my
> products, but I can only use it under the licensing terms of the purchase.
> There's nothing in the GPL preventing anyone from using GPLd code. In fact,
> it's explicitly available to anyone.
> 
> ciao,
> 
> der.hans
> -- 

I think Bob is referring to the fact that proprietary developers won't
use GPL'd libraries because then their code would be subject to the
GPL.And there is where the "viral" nature of the GPL comes in. M$
doesn't mind the BSD license at all because they can freely use BSD'd
code without their own code being subject to the BSD license. The GPL
gives them a rash because if they combine their own code with GPL'd
code, their code becomes subject to the GPL.

Of course, I'm approaching this subject from the point of view of a tech
writer and teacher rather than a developer, so I may not understand all
the details about how the GPL works in practice, but it seems to me that
the advantage is not in that proprietary developers CAN'T use GPL'd
libraries, but that they WON'T. Of course you can buy (or rent?!) code
from anyone, and as you said, use it under the terms of their license,
but the problem comes in when you combine their code with GPL'd code,
and their license and the GPL are incompatible. Then you have to
convince whoever owns the proprietary code to release it under the GPL,
or you can't release it at all.

For anyone interested,
http://www.gnu.org/licenses/gpl-faq.html#WhatIsCompatible
is a good place to start for specific information on this topic.

(Sorry if this is old news to some, but I'm fairly new to all this
stuff, and I was fascinated by what I found out in researching this
topic for the presentation.)