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Re: Bug#251885: ITP: cgal -- C++ library for computational geometry

Joachim Reichel wrote:
>> If the two licenses only applied to different libraries that linked to
>> each other, they would be compatible, because the scope of the LGPL
>> deliberately stops at the library boundary.  However, the LGPL requires
>> that all code which directly incorporates LGPLed code be LGPLed.
>> [...]
>> So any "work based on the library" must be licensed under the LGPL.
>> Since the QPL is not compatible with the LGPL, the entire work is
>> non-distributable.
> So what are the options for upstream?
> a) Relicense the code in a way that the work is redistributable, if
> possible DFSG-free.

That would work.  Note that if upstream likes the QPL, they would not
need to give it up completely; they could choose to dual-license the
work under the LGPL and the QPL, or under the GPL and the QPL, or under
any other Free license and the QPL.  As long as one of the license
options is a Free Software license.

> b) Split the library in (at least) two libraries, one (or more) for the
> LGPL code and one (or more) for the QPL code. (By "splitting", I mean
> creating two (or more) static/dynmaic libraries, not splitting the
> package itself.)

That would work, but the resulting package would go into non-free, since
it uses the QPL.

> c) What about clause 7 of the LGPL:
>>   7. You may place library facilities that are a work based on the
>> Library side-by-side in a single library together with other library
>> facilities not covered by this License, and distribute such a combined
>> library, provided that the separate distribution of the work based on
>> the Library and of the other library facilities is otherwise
>> permitted, and provided that you do these two things:
>>     a) Accompany the combined library with a copy of the same work
>>     based on the Library, uncombined with any other library
>>     facilities.  This must be distributed under the terms of the
>>     Sections above.

I think this would mean "accompany in the same package", so this is
basically the same as the previous option, except that you could also
provide a combined library.  Again, the resulting package would go into

>>     b) Give prominent notice with the combined library of the fact
>>     that part of it is a work based on the Library, and explaining
>>     where to find the accompanying uncombined form of the same work.
> For clarification, as I understand it:
> "Library" = LGPL-part of the code
> "library" = the dynamic/static library (including QPL code)
> Would this be another option? Is there a piece of software that actually
> uses this clause?
> d) What about an exception with respect to clause 2c) of the LGPL?
> Something similar like the GPL-waiver for libssl? This would also be an
> option, right?

Assuming the authors hold the copyright to the entire work (meaning that
they didn't incorporate any other LGPLed code), that would work.  See
http://www.gnu.org/licenses/gpl-faq.html#GPLIncompatibleLibs for details
on the exception, and modify it to work with the LGPL instead of the
GPL.  Again, this option would only let the package go into non-free.

- Josh Triplett

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