Experimental Physics and
Industrial Control System

john sinclair <[email protected]> · Tue, 18 Dec 2001 16:56:27 -0500 (EST)

True, this gets sticky.

However, I thought you could take any piece of GPL code and do anything
you want with it if you do not distribute it.

Also, I thought I could write this code and distribute it as GPL:

#include "cadef.h"

main () {

chid id;
int stat;

  stat = ca_search( "test", &id );

  stat = <some free qt function>(...);

}

I might also say something like: "oh, and if you want this code to link
and do anything useful, you must create cadef.h and some source file
that implements ca_search." But I don't think I'm legally required to
do so.

So, even if I'm using the free qt library, I should be able to write
code that calls these functions that are coincidentally the same as
the channel access ones. And to be more reasonable,
edm CAN be built and utilized without channel access using a set
of generic pv widgets that are included with the distribution. One
must simply implement a generic pv object (and in fact, a vsystem
user has done just this).

John Sinclair

On Tue, 18 Dec 2001, Andrew Johnson wrote:

> Korhonen Timo wrote:
> > 
> > Trying to figure out what can and what can not be done under different
> > types of licenses gives me a headache. It would be nice if somebody
> > clarified the license issues concerning various software components
> > that are used together with Epics (no, I am NOT volunteering to do
> > this!)
> 
> I Am Not A Lawyer (IANAL), This Is Not Legal Advice (TINLA).
> 
> Each site that is making software available to the EPICS community and the
> general public will almost certainly need to discuss this with their legal
> department to discover what your lab's requirements are.  I've been
> following the EPICS and Open Source licensing issues closely, and I'll
> explain what I personally think the situation is for labs who have signed
> an EPICS agreement and how this interacts with the GPL.  I may be
> completely mistaken though, don't rely on the contents of this message!
> 
> 1. The agreement that each lab signed with LANL gives labs the right to
> use and modify EPICS, but not to distribute it to anyone else in either
> source code or binary form.
> 
> 2. One of the key features of the GNU General Public License is that it
> does not permit the distribution of software linked to non-system
> libraries that are distributed under different licensing terms.  The EPICS
> Channel Access library falls into that non-system category, thus it can't
> be used in a GPL application.
> 
> 3. Note however that the GPL only controls the making of copies of
> licensed software, it can't control how you use a legally-obtained copy. 
> Thus it *may* be legal to write and use programs that combine GPL code
> with proprietary code, but you would need to be *extremely* careful what
> you actually distribute to other people (no binaries, nor source code that
> might have been contaminated by GPL source code).
> 
> 4. It *is* possible to license a program with the GPL that uses EPICS
> software, but the author must include an exception in the license allowing
> it to be linked with the relevant EPICS libraries (there is a section in
> the GPL FAQ at
> http://www.fsf.org/copyleft/gpl-faq.html#WritingFSWithNFLibs explaining
> how to add exceptions like this).  However you can only do this if you
> wrote the *whole* application yourself or you get permission to add this
> exception from all other authors.  You can't include any "standard GPL"
> licensed code in such an application, nor link with any other GPL
> libraries unless they also have the exact same exceptions in their
> licenses (even using dynamic linking needs you to include some information
> in your binaries from the GPL header files).
> 
> 5. That "however" in point 4 above means that (as far as I can see) it
> would not be legal to develop an EPICS display manager that used the Qt
> widget set unless you first paid for a Qt Professional Edition license,
> which doesn't hold you to the terms of the GPL.  According to the
> www.trolltech.com website you have to get that license at the start of
> your development too, you can't develop non-free software using the Qt
> Free Edition.
> 
> 6. The Gnome libraries are distributed under the LGPL, which does permit
> linking with non-free software, so a Gnome-based display manager could be
> written and distributed perfectly legally.  There are also other free C++
> widget sets available that may have compatible licenses.
> 
> Sorry if I've made your headache worse Timo, and unfortunately it
> currently doesn't look like we're going to be able to make it any easier
> in the near future either.  We discovered recently that EPICS has been
> ruled by the Department of Commerce to be subject to EAR99 export
> regulations, which makes it impossible to put EPICS base on a public
> website or license it as Open Source unless that ruling is changed - we'll
> say more about this in the New Year.
> 
> - Andrew
> -- 
> Perfection is reached, not when there is no longer anything to add,
> but when there is no longer anything to take away.
> - Antoine de Saint-Exupery
> 

John Sinclair
[email protected]
Oak Ridge National Lab
865-576-6362   865-574-1268 (fax)

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System