[Project-managers] editing external codes

[Laszlo Ladanyi]

On Sat, 7 Apr 2007, Matthew Galati wrote:

> FYI - cliquer is code for finding maximal cliques (its listed in COIN 
> resources):
>    http://www.coin-or.org/resources.html
>    http://users.tkk.fi/~pat/cliquer.html
> 
> I'll write the author and ask if they want the fix. That would be easier.

Yes, that would be the easiest solution. If they accept the patches you might
as well ask them to accept patches that make their code play nicely with C++
compilers...

> 
> Here's a related question that brings into question the same issues of 
> licenses and distribution.
> 
> My project is written in C++. Cliquer is C. I build cliquer with gcc and 
> the Makefile they provide - and it works fine. I call cliquer via extern 
> "C"...  However, cliquer, like alot of "old" C code I've seen has some 
> bad habits that don't play nicely with C++ compilers (like g++). For 
> example, cliquer's prototypes include the name "new" and "set" as a 
> variable name. A C++ compiler won't have that. The way I get around this 
> kind of thing is to write an "interface" header where I wrote my own 
> prototypes for whatever I actually call from my code, then extern "C" 
> {#include "cliquerInterface.h"}. Then, of course, I distribute my 
> cliquerInterface.h. I presume this is all ok wrt to licenses. But, it 
> gets a little sticky when I start using macro defines that come from the 
> original cliquer.h. Since I am not including cliquer.h, but rather 
> cliquerInterface.h, I have to copy the macros over too - which for some 
> codes is a bunch of stuff. Is that now a license issue? I am taking bits 
> of the GPL code and distributing it with my code in my interface header.

IANAL, but this definitely sounds sticky. My gut feeling would be that if a
small patch accomplishes what is needed to properly compile the code then
distributing cliquerInterface.h under the CPL is a violation of the GPL (you
just changed license without the permission of the copyright holder). If the
patch is larger than the original file then cliquerInterface.h is
significantly different so that you are the copyright holder, so you can
release it as you want. But as I said, that's only my feeling and the law
might say otherwise... 

So the cleanest (legally) solution is if they accept all the patches you make.
Short of that you can host a copy of cliquer with the patches (giving them
credit, of course), distribute it under the GPL, and link against that version
of cliquer. This is perfectly OK, you have every right to fork a GPL code. The
only sticky part is: where do you host it? You can certainly create a
sourceforge project. Hosting it on COIN might be possible, too, but I have no
idea what is the policy for such a project. It never came up and may or may
not fly. In conclusion: try to convince the authors to accept patches :-).


> 
> This license stuff all seems very messy to me. Why can't I add GPL code 
> in my COIN code and just distribute my stuff GPL and CPL and 
> 'whoever-wants -it-feel-free-to-use-it- PL'.

You haven't talked much to lawyers yet, have you? Bless your innocent
heart... :-).

> 
> Matt

--Laci

> 
> 
> > Hi Matt,
> >
> > I don't know what Cliquer is, but the ideal case would be that you get 
> > the Cliquer developers to include your changes in a new version.  They 
> > would probably be grateful to get fixes that make it work on Windows...?
> >
> > Otherwise, you could include patch files in your distribution and tell 
> > users that want to use Cliquer on Cygwin how they have to apply the 
> > patches to Cliquer code that they download separately.
> >
> > Andreas
> >
> > On Fri, 6 Apr 2007, Matthew Galati wrote:
> >
> >> In one of the examples in my project DECOMP, I use a GPL licensed 
> >> code (Cliquer). In my INSTALL, I provide the user the option to 
> >> download and link with it or not (and give them www). It works fine 
> >> with unix flavors, but Cliquer was never written to run on Windows. I 
> >> can fix the Cliquer code to compile in Windows with a few ifdef's.
> >>
> >> But, now how does this work? I know I am not suppose to distribute 
> >> Cliquer via svn. If so, I could just provide my "adjusted" Cliquer.
> >>
> >> I guess, this is a general question -- how do I distribute 
> >> derivatives of other external codes to be used with my COIN project?
> >>
> >> Thanks,
> >> Matt 
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