[Foundation-l] Requirements for a strong copyleft license

[Anthony]

On Dec 1, 2007 8:22 PM, Erik Moeller <erik at wikimedia.org> wrote:
> * IMPORTANT - I believe it should allow mixing of similar licenses,
> e.g. CC-BY-SA into BSD -- the Definition of Free Cultural Works
> endorsed by Wikimedia could be a guideline as to which licenses can be
> mixed: http://freedomdefined.org/Definition
>
Can't you already mix a copyleft license (like GFDL) with a free
non-copyleft license (like BSD), so long as the combined work is
released under the copyleft license?  If so, this would only be useful
for mixing with other copyleft licenses, which is arguably not all
that important (especially once the wiki-world migrates away from the
GFDL), and can be accomplished by dual/multi-licensing (if the
author(s) desire(s)) anyway.