Copyrights, Licenses and CDDL Illustrated
By chandan on Sep 18, 2006
At the time CDDL was being introduced, I wanted to write an illustrated version of it. Merely because hardly anyone would read the full license text. Even if they did, I doubt 9 out 10 would have understood it completely. A recent CDDL/GPL misunderstanding that made news and started flame wars, prompted me to revisit an old illustration.
One approach is to understand copyrights, patents and licenses. The rights in copyrights are mainly rights to copy, modify, distribute, perform and display some 'work'... Patents protect ones right to use, manufacture or sell an 'idea' ... License is a set of rules and permissions... Other approach is to compare familiar licenses with CDDL.
This matrix tries to express some proprietary-EULA, GPL, CDDL and BSD licenses in terms of the rights in copyrights and patent rights. A green tick and red cross are self explanatory. A grey "~" means that the license does not say anything - mostly it is an implied OK.
Now lets compare and contrast GPL, CDDL and BSD licenses with respect to come common needs of developers who copy, modify or distribute a piece of software:
A common misconception is about CDDL and GPL incompatibility. (Incompatibility in the sense: to combine two source files, one under GPL and another under CDDL, to create a common executable.) GPL is incompatible with most licenses like Mozilla Public License, Apache, and CDDL. GPL wants you erase those licenses and use GPL in that place, where as these licenses do not permit erasing them. Hence the incompatibility deadlock.
Disclaimer: I am not a lawyer. I have gone to a law school, because my bank had a branch there. I have tried to keep these diagrams as factual and error free as possible. If there are errors, blame them on the tongue twisting legal-speak of license terms or please point them. These tables do not represent everything a license would say, merely hopes to capture their essence.