Experimental Physics and
Industrial Control System

"J. Lewis Muir" <[email protected]> · Wed, 22 Oct 2014 13:20:29 -0500

On 10/22/14 12:29 PM, Emmanuel Mayssat wrote:
> It seems that the engineer think of the GPL as the default.  Meaning,
> "I don't know anything about licensing but because the GPL is a
> popular, I will use it."  But does anyone understand what the GPL
> is? It is an ideology.

Hi, Emmanuel.

I do, and I think many others do.  But you might be right that some
don't.

> Now about the GPL.
> The GPL forces derivative work (add-ons, extensions, or rewrite)
> to be GPL as well. (not any other license I want and not a GPL +
> modifications) Additionally, the GPL FORCES contributors to make the
> source code of their contribution available for free.  The enforcement
> is key. The GPL means the author of the original software wants to
> promote the ideology of forever free open source software.  The GPL is
> regarded as business unfriendly as it removes FOREVER a major revenue
> stream.

I would say *some* regard the GPL as business unfriendly.  Obviously,
Red Hat, etc. are making a fine business using GPL software.

> The LGPLv3 fix that last issue.
> With the LGPL, the core software libraries are open-source and free,
> but additional libraries or high-level applications HAVE THE OPTION of
> being distributed under another license. CSS and EPICS Qt framework
> are good candidates for the LGPLv3.

Not quite.  I think the issue you're talking about with the GPL is that
any program that *links with* a GPL program (library) must itself then
be GPL (or GPL-compatible).  This is because the GPL considers your
program to be part of the GPL program if you've linked with it.  The
LGPL specifically allows you to link your program with an LGPL program
(library) without this requirement.  But I'm pretty sure the LGPL still
has the rules about making changes to a program (library) licensed under
it: if you make a change to an LGPL program (library), you have to make
those changes publicly available.

Note that if you don't link with a GPL program (library), your program
doesn't have to be GPL.  So, for example, if you use fork and exec to
invoke a GPL program, the GPL considers them to be separate programs,
and so your program would not have to be GPL.  This could be simply
running some program, or it could be running a "plug-in" program.

Regards,

Lewis

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System