Re: GFDL / CC by-sa compatibility

I still don't see the legal distinction.  Creators of derivitive works 
aren't *required* to release those derivitives under all later 
versions.  However, if the original work is released under later 
versions, then they are *allowed* to release derivitives under those 
later versions.  Looking at the text again:

"If the Document specifies that a particular numbered version of this 
License "or any later version" applies to it, you have the option of 
following the terms and conditions either of that specified version or 
of any later version that has been published (not as a draft) by the 
Free Software Foundation."

It seems to me that that is merely restating the obvious.  Looking at 
the Modifications section:

"You may copy and distribute a Modified Version of the Document under 
the conditions of sections 2 and 3 above, provided that you release the 
Modified Version under precisely this License, with the Modified Version 
filling the role of the Document, thus licensing distribution and 
modification of the Modified Version to whoever possesses a copy of it."

So if you create a derivitive under version 1.2, you have to license 
that derivitive under 1.2.  But it does not say that you cannot 
simultaneously create a derivitive under version 1.3 and license that 
derivitive under 1.3.  You say that the GFDL "specifies that 
[derivitives] can only be spread further under the same license, not a 
later version."  But the GFDL does not say that.  It says you *may* 
spread derivitives if you release them under the same license.  But it 
does not say you can't spread derivitives if you release them under a 
different license.  And it also doesn't say you can't do both, release 
them under the same license, and under a different license.  You'd need 
separate permission from the original copyright holder to do either of 
the latter two, of course, but this separate permission is granted in 
the license grant, which states that you can use this license, or any 
later version.

I'd like to see where you're getting the idea that you can only license 
derivitives under a single license.  Because this is plainly 
contradicted by the very text of the GFDL.

>This works for original works; it does not work for copied and derived
>works, since they have been copied under rights gotten from a certain version
>of CC (or GNU/FDL), which specifies that it can only be spread further
>under the same license, not a later version.
>
>Andre Engels
>  
>