[postgis-users] Is PostGIS effectively LGPL?

Bruce Momjian bruce at momjian.us
Fri Dec 23 08:35:08 PST 2016

On Fri, Dec 23, 2016 at 05:14:07PM +0100, Sandro Santilli wrote:
> On Wed, Dec 21, 2016 at 03:25:28PM -0500, Bruce Momjian wrote:
> > 
> > Well, imagine someone writes a closed-source server-side function that
> > calls PostGIS functions.  Is that allowed?
> It is allowed to write the function, but if such function is *distributed*,
> then it will need to be distributed under the GPL license.

Yes, that is my reading of the GPL too, though I think only if PostGIS
is distributed to the user with the function.

The FAQ is misleading on this point:

	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.

Obviously, modifying PostGIS is not the _only_ case in which
developer-generated source code must be distributed.

> > I think the dynamic linking thing has always been unclear so clarifying
> > it in the FAQ is fine, if in fact that is what is says, and other
> > projects have done this clarification.  Right now I am not sure where
> > PostGIS is on this issue.
> To me using SQL from plpgsql or sql to call PostGIS is not to be
> considered linking, while using DirectFunctionCall or directly
> calling liblwgeom functions is.

Agreed.  I think the two cases that are linking are server-side C
functions that call PostGIS functions and the Postgres backend binary. 

I don't know how this interacts with whether the user downloads PostGIS
independently, but this clearly is not covered in the license FAQ.  I
guess it isn't an FAQ if I am the only one asking about it, though.

  Bruce Momjian  <bruce at momjian.us>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

+ As you are, so once was I.  As I am, so you will be. +
+                      Ancient Roman grave inscription +

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