[ILUG] GPL and LGPL

[Paul Jakma]

On Fri, 22 Apr 2005, Michael Conry wrote:

> As I understand it, if the library is licensed under the full GPL,
> then applications linked with it must also be GPL.  If it's 
> licensed under the LGPL, then that requirement is not imposed 
> (although if you extend the library, then the extended/modified 
> library must also be LGPL (maybe the changes could acceptably be 
> GPL licensed also?)).
>
> http://www.gnu.org/philosophy/why-not-lgpl.html The above link 
> gives info on when Richard Stallman would recommend to use GPL/LGPL 
> (in that case Library-GPL, superseded now by the Lesser-GPL). 
> Basically, the suggested criteria is that if the library is 
> revolutionary, one-of-a-kind, then keep it GPL to help other GPL 
> developers at the expense of proprietary work.  If there are many 
> proprietary (or BSD-licensed) alternatives, then LGPL will be 
> better in order to get the maximum user-base.

An interesting one to consider:

Say you have a well-known and widely used GPL library, well-known 
enough that proprietary applications have on occssion used it and 
been forced to desist or relicence their application.

The GPLness of this fairly ubiquitous GPL library bothers the BSD 
camp enough to implement their own API compatible version of it. So 
now applications can (at compile time) link to either library. If the 
BSD licenced one, clearly there is no need for the application to be 
GPL licenced.

Nothing interesting yet. However, what if the replacement BSD library 
is made binary compatible? Such that a proprietary application could 
run-time to either the GPL or the BSD licenced library (indeed - it 
wouldnt be the application to decide which).

Does the existence of this BSD licenced, binary compatible library 
render the GPL's reach across the library interface and into the 
application void?

If it does, was that reach ever valid? If so, why?

(Ie, i suspect the GPL's purported ability to reach across well 
defined interfaces to possibly not have much merit).

regards,
-- 
Paul Jakma	paul at clubi.ie	paul at jakma.org	Key ID: 64A2FF6A
Fortune:
Many are cold, but few are frozen.