CDDL says: Source code must be licensed under CDDL.
GPL says: Source code must be licensed under GPL.
If you follow the conditions of GPL, you are violating the condition of the CDDL. If you are following the conditions of CDDL, you are violating the GPL. Basic binary logic.
To add: "the engineers who had written the Solaris kernel requested that the license of OpenSolaris be GPL-incompatible". A license is really just an written intention of the author on what conditions copyright law restrictions may be legally ignored. In this case, those wishes had a very explicit intention. However those using the license today has had a general change of heart, and those with GPL interest has a general stance that no FOSS project will ever sue an other FOSS project over license incompatibility. As such, the risk of lawsuit is really just a company suing an other company under the technicality of incompatibility.
Naturally some organizations won't intentionally break copyright law just because no one will sue.
Neither license forbids mixing with other licenses. As long as the demands of both are met, they can apply to the same source code.
>If you are following the conditions of CDDL, you are violating the GPL. Basic binary logic.
Relationship between licenses can be transitive but not commutative.
As far as I know CDDL allows using with code under GPL but GPL does not allow using code under CDDL. CDDL copyright owners have no case, GPL copyright owners have.
The question is: If I'm incorrect, what in CDDL prevents using with GPL?
If CDDL has no issue with GPL conditions, then follow the GPL and everything is fine.
CDDL has this text: "Any Covered Software that You distribute or otherwise make available in Executable form must also be made available in Source Code form and that Source Code form must be distributed only under the terms of this License"
So you take some CDDL code, and some GPL code, and you put that whole new source code tree under GPL in order to fullfill the GPL license condition. Are you then in compliance with the CDDL code? My concussion is that you are not, as that would be in conflict with the above condition of the CDDL. The source code tree would not be "distributed only under the terms of this license".
I take a CDDL licensed source code file. I take a GPL licensed source code file. I add inline the GPL licensed code to the CDDL licensed file, and release an executable form of the result. In order to comply with the GPL I then give out a single source code file under the GPL license terms with the code from the two files.
Is this in compliance with the CDDL terms and conditions?
This stackoverflow question have some good points (notably, the accepted answer, and the bit about limitations - the CDDL section 6.2, for example revokes the CDDL in case of patent infringement, something that might be considered an "extra limitation" under the GPL (you're not allowed to add additional limitations to either the GPL or the CDDL). As such, the CDDL might be incompatible with the GPL up to and including v2 - while GPL3 might also be incompatible with the CDDL):
Also, the SO answer mentions consumer protection laws - but AFAIK they generally only apply to consumers - not businesses. So the GPL 0 clause might be void in many jurisdictions for individuals but still valid for businesses.
The only issue I'm aware is that mixing the two would violate GPL.