Decision: CC-BY / GPL

Daniel Carrera dcarrera at math.umd.edu
Fri Mar 11 07:04:02 EST 2005


Branko Collin wrote:

> "part" --> "party"?

Yeah. Thanks.


> There was some discussion about dual licensing in the past (look at 
> the archives).

That's interesting. About the ShareAlike license not being compatible with 
dual licensing. I wonder why the same thing doesn't happen with the GPL. 
Well, in any event, thanks for the note. I'll be careful not to use the SA 
unless I know what I'm getting into.

> "My (admittedly inexpert) understanding is that a dual-licensed 
> derivative work would not meet the requirements of by-sa 1.0,

If it's your own work, you can slap any license you want on it. Including 
a dual SA/FDL. But what this person wrote suggests that the licensees will 
be forced to pick one or the other.

But I still wonder, why doesn't that happen with the GPL ?

But in any event, I don't have to think about this. I'm not going to use 
the SA license.

> Although strictly speaking you are not dual-licensing it, it seems 
> like you are forcing any down-stream authors to choose between CC-BY 
> or GFDL

I checked the language of the Perl license, and they wrote it the same 
way. They say "or". And people have been re-distributing Perl using both 
licenses at the same time for 20 years. And almost all the modules on the 
CPAN archive do the same.

IANAL, but I figure that the laguage is okay. This is my interpretation:

Suppose I gave you two copies of the file. One under the GPL and one under 
the CC-BY. Then you have both licenses. You can then give the unmodified 
file to someone else, under either license. Or you can give them two 
copies, one under each. In practice, so far, you are still handing out the 
file with both licenses.

Now, what happens if you make a modification? Well, suppose the 
modification is compatible with both licenses? Then you still have 
permission to distribute it under the GPL, and you *also* have permission 
to distribute it under the CC-BY. So, you can still give out two copies of 
the file, one under each license.

So, it looks like, as long as the modifications you make are allowed by 
both licenses, you can, in effect, treat the license tandem as one unit. 
You only lose this when you want to do something that is allowed by one 
license and not the other.

So, it seems to me that dual licening really does work.

Cheers,
-- 
Daniel Carrera          | I don't want it perfect,
Join OOoAuthors today!  | I want it Tuesday.
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