From: Mark Wilson <mwilson13@...>
Date: 2003-02-16T15:17:40+09:00
Subject: Re: GPL question


On Saturday, February 15, 2003, at 11:12 PM, Jim Weirich wrote:

> On Sat, 2003-02-15 at 18:06, Mark Wilson wrote:
>> The dual license means that you can pick one or the other as the basis
>> for your use of the Perl module. Because of differences between the
>> Artistic license and the GPL you cannot pick both for purposes of your
>> derivative work.
>
> If the original work is licensed under the Artistic and GPL, why can't
> the derivative work also be licensed in the same way?  I don't
> understand why, could you explain?  Thanks.

It's probably a difference that makes no difference. There are two 
licenses in Daniel's question: the first is the license of the Perl 
module and the second is the license of the derivate work he creates. 
Because the Perl module can be used pursuant to the Artistic License or 
the GPL, as a technical matter you choose one or the other at your 
discretion. Note that the dual license is actually "or" and not "and".

If you distribute a derivative work pursuant to anything other than the 
GPL only, then you've chosen to use the Artistic License for the Perl 
module. So it doesn't really matter, I suppose. You still have to 
follow the terms of the Artistic License, which, unlike the GPL, 
permits incorporation into a commercial and/or closed source product.

Where it does matter is if something is GPL only. Then your derivative 
work can only be distributed pursuant to the GPL (or pursuant to a 
separate license with the copyright owner of the program). Of course, 
for many of the most useful GPL programs, there are many authors and 
therefore many copyright holders and one would have to get agreement 
from all of them to license other than through the GPL.

Finally, Ruby's license is closer to FreeBSD license, in that you are 
free to incorporate the code into your own commercial product and close 
off the source to what you wrote, if you wanted to.