On 10/16/06, gwern branwen gwern0@gmail.com wrote:
Roger, could you expand on this? I'm not following how it works. I understand that dual-licensing works for software because companies may not want to copyleft their work, and because just source code isn't actually all that useful minus maintenance and support and documentation and other things that companies like Redhat provide for money, but how does this apply to regular old content? Is the GFDL as 'viral' as the GPL in regard to modification and incorporation, and is not being GFDL valuable enough to various parties that the relevant corporations would still realize their desired sums?
I'm not roger, but...
GFDL, CC-By-SA, and the GPL (as well as many others..) are copyleft licenses.
http://en.wikipedia.org/wiki/Copyleft
Copyleft licenses ensure that all decedents of the copylefted work remain at least as free (but potentially no more free) as the original copylefted work.
The result is that if someone wants to make a derived work starting from a copylefted base they may not deny downstream recipients the same rights which they received.
In the future, please avoid calling the share-alike nature of copylefted works "viral": Because nothing forces you to make use of the copylefted work of others the comparison to others, and no violation to force you to open your own works (rather, a failure to option in the face of a violation of a copyleft licenses leaves you open to prosecution for copyright violation), it is inaccurate to use the derogatory term "viral" to refer to copyleft licenses.
As far as dual licensing, the GFDL and CC-By-SA are not compatible. There used to be a larger philosophical schism between the two licenses (for example, in terms of the intensity of DRM protection) but the new GFDL drafts (Esp the SFDL) substantially reduce the real incompatibility (by making unfortunate changes, such as leaving the GFDL with less DRM protection than CC licenses) .. but the gratuitous incompatibility remains and is not likely to be resolved due to an increasing disconnect between RMS (http://en.wikipedia.org/wiki/Richard_Stallman) and the creative commons (which happily endorses unfree licenses like CC-By-NC-ND which inhibit read write culture, along side acceptable free ones like CC-By-SA-1/2.0).
So long as the GFDL (or really the SFDL) is going to be functionally equal but gratuitously incompatible with CC-By-SA-2.0, the dual licensing makes sense....