[Erik Erlandson <ee...@redhat.com>]

Lately I have been looking into licensing issues surrounding the
possibility of Apache Spark publishing "official" reference container
images. For context, this was driven primarily by the recent upstreaming of
a Kubernetes scheduler back-end, which by nature runs on container images
(however, it would also have utility for Mesos, etc)

Apache Legal has already issued some official positions, to the effect that
publishing a container image in and of itself is legally fine, provided
some criteria are met. The current state of thinking on this topic is
influenced by the LEGAL-270 Jira
<https://issues.apache.org/jira/browse/LEGAL-270> which can be summarized
as:
* A container image has the same legal status as other derived distributions
* As such, it is legally sound to publish a container image as long as that
image corresponds to an official project release
* An image that is regularly built from non-release code (e.g. a
'spark:latest' image built from the head of master branch) would not be
legally approved
* The image should not contain any code or binaries that carry GPL
licenses, or other licenses considered incompatible with ASF.

It is this last bullet point, having to do with GPL, that I have been
drilling down on.  Richard Fontana recently wrote a very interesting
article on the topic of GPL and its implications for container images:
https://opensource.com/article/18/1/containers-gpl-and-copyleft

The gist of the article is that there are important exceptions, or
"firewalls," that prevent the GPL from infecting other licensing in many
common cases.  I wrote up some of my thoughts on the subject here:
https://docs.google.com/document/d/1syUnhiFm8-H0bWsWFyIL3NzedDCvoJEIwWRkEORho0s/

My IANAL take on all this; is that in many cases the mere presence, or even
use, of GPL tools is not toxic to an ASF project if it were to publish
official reference images.

Assuming I am correct*,* I believe that there is an opportunity for ASF to
reduce future friction by adopting some additional official opinions on
allowing ASF projects to publish official reference container images, as
long as those container images abide by certain copyleft clauses such as
"mere aggregation", and the gcc/glibc exception, classpath-exception, etc,
that prevent copyleft contamination of Apache licensed projects.

Since I am far from an expert on software licensing law, I am very
interested in Apache Legal's opinions on these ideas.

Cheers,
Erik