[cc-devel] License Compatibility Checker using ccREL

Vítor Baptista vitor at vitorbaptista.com
Fri Sep 17 20:37:29 EDT 2010


Hi,

My name is Vitor, I am a brazilian CompSci student. I'm in my bachelor's
last semester, and I'm building a free license compatibility checker as my
thesis. I would like to ask some questions, any help will be greatly
appreciated. Sorry for the long e-mail.

* If I were to describe the "default" copyright schema (as in "I made
something but haven't made any explicit license"), I should simply use ccREL
with no permissions, no requirements and no prohibitions? With all
attributes unset?

* I'm thinking about how I could, using ccREL, check if two licenses are
compatible. At a first glance it seems that I could simply:
1. You can't give more permissions than those that were given to you (but
you can give less);
2. You can't remove prohibitions (but you can add);
3. You must comply to the requirements of each and every part of your
software (and might add some more);

These seems to work for the simple case (no copyleft/sharealike parts). But,
before I go into that, there're two attributes that I find confusing.
1. High Income Nation Use -- If I don't this permission, what does it means?
That I can't distribute the work in the USA, for example? I couldn't find
any licenses that uses this (not CC licenses, at least);
2. Sharing -- Also, couldn't find no licenses using it. It means that I may
create a derivative work and sell it, but can't sell the unmodified program?

These attributes seems more prohibitions than permissions to me. I don't
think I'm understanding them fully.

* For compatibility between copyleft licenses, there're x rules:
1. Is it the same license? If so, they're compatible; if not, use rule 2;
2. Are they explicitly compatible? For this, I have to use a pre-calculated
database like "GPLv2+ is compatible with GPLv2 or any later version", etc.
(maybe it'll be nice to have an extension to ccREL to support this? (Thanks
RDF))

If there's a Lesser Copyleft license, my program (as I think of it) cannot
decide, so just tell the user to contact a lawyer. If there's a ShareAlike,
use:
1. Compatible if it's just a newer version of the license;
2. Compatible if it's the same version but for a different jurisdiction;
3. Incompatible if not.



Any thoughts or ideas about this? Does these rules makes sense?

Thanks in advance,

-- 
Vítor Baptista
Comissão Organizadora
IV Encontro de Software Livre da Paraíba
6, 7, 8 e 9 de Maio de 2010
Estação Ciência, Cultura e Artes Cabo Branco
João Pessoa, PB.

http://www.ensol.org.br
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