[cc-licenses] Most important feature: GPL-compatibility

Rob Myers rob at robmyers.org
Thu Dec 29 05:21:48 EST 2011


On 28/12/11 21:44, Francesco Poli wrote:
> 
> In these cases, having parts of the game licensed under the terms of
> the GNU GPL and parts under the terms of CC-by-sa (or CC-by) may create
> compatibility issues and/or legal uncertainty, which may significantly
> slow down the development of the game itself.

Are there any examples of this happening?

Game assets being under an appropriate CC license shouldn't affect game
engine code licensing.

> How can GPL-compatibility be implemented into CC-v4.0 licenses?
> 
> I think the only possible approach is including an explicit one-way
> conversion clause.

The MPL 2 beta has been mentioned as an example for how this could work:

https://mpl.mozilla.org/wp-content/uploads/2011/03/MPL-2-B2-plain.txt

>   * CC-by-sa-v4.0 should include an explicit one-way conversion clause
> that would allow redistribution of the work under the terms of the GNU
> GPL version 2 or any later version

The current version of the GPL is 3, so the current CC licenses should
be compatible with GPL 3.

MPL 2B2 also explicitly allows compatibility with the LGPL and AGPL. CC
licences should be directly compatible with the AGPL at least.

>   * CC-by-v4.0 should include an explicit one-way conversion clause
> that would allow redistribution of the work under the terms of the zlib
> license: http://www.gzip.org/zlib/zlib_license.html
> 
> I chose the zlib license, since it's a simple permissive non-copyleft
> license which is GPL-compatible. Another similar license could be
> chosen as well, if considered more suitable (for example the Expat
> license: http://www.jclark.com/xml/copying.txt   or the 3-clause BSD
> license: http://www.debian.org/misc/bsd.license).

Why would this be needed? Work under BY and MIT or X11 (for other
examples) can be used together in derivatives/adaptations without
conflict. Unlike copyleft licences, permissive licenses do not have the
requirement that derivatives be placed under the same license and so
they do not have the same compatibility problems as conflicting copylefts.

- Rob.


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