[postgis-tickets] [PostGIS] #3606: CGAL/SFCGAL/PostGIS License Implications Clarification Documentation

[PostGIS]

#3606: CGAL/SFCGAL/PostGIS License Implications Clarification Documentation
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 Reporter:  thx1138                            |      Owner:  pramsey
     Type:  enhancement                        |     Status:  new
 Priority:  high                               |  Milestone:  PostGIS 2.3.0
Component:  postgis                            |    Version:  2.2.x
 Keywords:  license sfcgal cgal documentation  |
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 I'm preparing to upgrade an installation of Postgis in the near future and
 am excited to try out SFCGAL due to its robustness improvements for
 PostGIS functions. However, I was extremely confused by the astoundingly
 complicated dual GPL/LGPL license terms of CGAL upon which SFCGAL and
 Postgis now depend.

 The Postgis FAQ [http://postgis.net/docs/PostGIS_FAQ.html#license_faq]
 implies that there should be no issues for a commercial app -unless that
 app actually modifies the postgis source:

   3.19.

   I am releasing software that uses PostGIS, does that mean my software
 has to be licensed using the GPL like PostGIS? Will I have to publish all
 my code if I use PostGIS?

   Almost certainly not. As an example, consider Oracle database running on
 Linux. Linux is GPL, Oracle is not, does Oracle running on Linux have to
 be distributed using the GPL? No. So your software can use a
 PostgreSQL/PostGIS database as much as it wants and be under any license
 you like.

   The only exception would be if you made changes to the PostGIS source
 code, and distributed your changed version of PostGIS. In that case you
 would have to share the code of your changed PostGIS (but not the code of
 applications running on top of it). Even in this limited case, you would
 still only have to distribute source code to people you distributed
 binaries to. The GPL does not require that you publish your source code,
 only that you share it with people you give binaries to.


 However looking at the CGAL website[http://www.cgal.org/license.html] they
 mention the following:



   The GPL (v3+) is an Open Source license that, gives you the right to
 use, copy and modify the code freely. If you distribute your software
 based on GPLed CGAL data structures, you are obliged to distribute the
 modifications of CGAL you made, and you are furthermore obliged to
 distribute the source code of your own software under the GPL.

 ...and their product licensing
 page[http://geometryfactory.com/products/licenses/] shows even more
 confusing information:

   Industrial Development License

   This is the license for industrial users who '''integrate our software
 components in applications that they commercialize or that they use
 internally, for example in a production chain'''.

   The price of a component is independent from the numbers of developers
 in the same company using it. It is a one shot fee, that is there are no
 royalties to pay when you distribute your software with our components
 inside.

 Taken together, this information leads a person not familiar with the fine
 intricacies of software licensing (like myself) to the following possible
 contradictory conclusions:

 1. It's safe to use ALL SFCGAL functions in a commercial PostGIS app
 regardless of whether or not the underlying CGAL code is GPLed unless you
 are modifying the cgal or Postgis source code.

 2. It's safe to use ALL SFCGAL functions in a commercial app because the
 PostGIS functions are only pulling from the LGPL portion of CGAL

 3. It is not safe to use any SFCGAL function in a commercial PostGIS app
 unless you look at each individual function definition in PostGIS/SFCGAL,
 trace it to the CGAL source files and determine if those files are GPL or
 LGPL.

 PostGIS with SFCGAL support is now widely available on Ubuntu via a simple
 apt-get and I don't imagine most developers would expect that they would
 be required to release all of their app source code or pay $10,000+ if
 their app runs {{{select st_union(geom)}}} with an SFCGAL backend on their
 db.

 '''TL;DR; Given that PostGIS is widely used, I think it would be worth
 clarifying the SFCGAL licensing situation and posting a clear answer on
 the FAQ and in the documentation. Also, if the use of individual SFCGAL-
 based functions would require purchasing a commercial license or releasing
 source code, I think it would be worth adding that information to the
 applicable function docs so that it is clear to users.'''

--
Ticket URL: <https://trac.osgeo.org/postgis/ticket/3606>
PostGIS <http://trac.osgeo.org/postgis/>
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