[postgis-devel] Re: [Bizgres-general] Bizgres MPP and PostGIS

[Markus Schaber]

Hi, Luke,

I'm CC'ing this mail to PostGIS-Devel, as I think that Strk, Paul and
others may enlighten this discussion with their standpoints.

@postgis-devel: The discussion was about legal (GPL vs. proprietary
extensions) and technical (Multithreaded backends) problems of running
PostGIS under Bizgres / Bizgres MPP.

As far as I can see, Bizgres itsself does not impose any problems (as
it's pure BSD license like PostgreSQL itsself), but MPP has proprietary
extensions.

Luke Lonergan wrote:

> The complication as I understand it is that Postgres goes through a patch
> process to get the PostGIS functionality into it.

As far as I understand the current build process, recent PostGIS
versions being build against recent PostgreSQL servers using recent
toolchains only needs the pg_config output, and the "official" headers
served by pg_config.

The last "patches" against the server I heard from were changed linker
flags during Postmaster compilation, due to deficiencies in the build
tools. It was needed to link explicitly against libstdc++, because
PostGIS pulls libgeos as a dependency (which is in C++). However, the
dynamic loaders in current GCC/glibc environments can cope with that
without any patches.

> At that point, there is
> PostGIS source code in the merged entity, which transfers the GPL
> restrictions to the source.  At this point, any compiled product is subject
> to those restrictions, which force the inclusion of the source code and the
> inability to charge for the resulting binaries.

No, there is no inability to charge for resulting binaries. You can
charge as much as you want.

And there are alternatives to directly including the source with the
binary.

One can argue about the GPl, and it clearly has its serious flaws, but
please don't circulage false Myths about the GPL.

> I think that this doesn't preclude an arrangement with the holder of the GPL
> license for a special version that we could incorporate into Bizgres MPP.

AFAICs, several people contributed to PostGIS, not all of them having a
contract with refractions. And there's no "copyright assignment"
process, unlike e. G. the GNU projects. So you'll have to find at least
all substantial contributors, and ask them for permission.

Most of them should be noted in the file headers / copyright notices,
but nobody will want to guarantee that.

> We are interested in supporting PostGIS with MPP because the operations it
> performs would likely benefit greatly from the parallelism of the MPP
> kernel. 

I agree with that.

However, most of the PostGIS code is not even thread safe from my
knowledge, and far from explicitly parallelized.

> The main impediment so far has been our limited development
> personnel - all are focused on features desired by our data warehousing
> customers.

I see. And as long as you don't have hordes of potential PostGIS
customers knocking on your door, that won't change. :-)

> There are a couple of ways we can proceed if we have enough demand for
> PostGIS MPP:
> A) We can make a side arrangement with the PostGIS developers to support a
> bundle, perhaps even have them do the porting work.

Such an arrangement may be possible.

> B) Perhaps we can perform a service that compiles the code for each PostGIS
> MPP customer, places the source code in escrow and we charge an annual
> maintenance fee.  I'm not sure if this is still compatible with GPL, but it
> seems similar to RedHat and other's approaches. 

Maintainance fees are (as well as fees for the binary) completely legal
under the GPL. That's not what the GPL wants to restrict.

> The biggest difference is
> that the source code is not made available to the general public as it is
> with RedHat, but only to the support customers through the limited
> conditions of an escrow.

Here's a problem. Due to the GPL, you may not hinder your customers from
redistributing the source. They must have at least the rights the GPl
guarantees them, including redistribution under GPL.

One possible idea to workaround this is a binary compatible interface.
As long as MPP and PostgreSQL are binary compatible, it could be
possible to dynamically link a Bizgres/PostgreSQL-compiled PostGIS into
an MPP backend at the customers site.

In my eyes, this is the same case as proprietary applications runnign
under glibc/Linux, or GPLed applications under Windows / commercial
unices. However, IANAL.

> Of these two, I far prefer (A).  Even better would be to have the PostGIS
> people change their license to LGPL or BSD.

As far as I know some of the main PostGIS developers, they're unlikely
to agree to such a step, and I personally (and my employer who founded
my small contributions) tend to see LGPL as acceptable, but not BSD license.

Another possibility could be to add an explicit linking exception
permitting linkage against non-GPL compatible backend extensions to the
PostGIS license, as some other projects (including libgcc) have. (Note
that this is different from the LGPL.)

Thanks,
Markus