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CDDL is equally incompatible with both GPL versions.
Incompatibility is because GPL and CDDL are both copyleft licenses and neither permit re-licensing code to any other license; CDDL code is availabe under CDDL only and GPL code is available under GPL only. GPL's copyleft is wider and stronger, it requires all derivatives and extensions of GPL'd code to be under GPL-compatible license as well, while CDDL apply only to specific source files and allows proprietary extensions (or open source, as long it is not GPL). There are lot other differences, but this is biggest.
So, ZFS becomes part of kernel when is merged, and whole kernel is GPL. Since CDDL does not alow re-licensing to GPL, it can't be merged.
All this is not by mistake. Sun have chosen GPL incompatible license for OpenSolaris and ZFS on purpose. Danese Cooper is the one who actually wrote CDDL, and she said on Debian conference in 2006 that special requirement for was that license must be GPL-incompatible. Here is the link http://caesar.acc.umu.se/pub/debian-meetings/2006/debconf6/theora-s...
PS: Watch at 11:30 and later.
So whole crack-pot idea of changing Linux to CDDL is crazy. Day when Linux switches to CDDL would be the day when ZFS switch to something else and Linux would be stuck with oldish version.
Not like that is going to happen, Solaris is going proprietary anyway.
Edited 2010-06-08 08:56 UTC
Thanks for the explanation.
What makes you think this? What would it even mean to "go proprietary"? Scrapping the CDDL? Really? To me it seems like the open-source nature of Solaris is the only thing keeping it vibrant. HP/UX and AIX may still have plenty of customers, but the question is, what percentage are just legacy? With Solaris I actually see some potential for growth, precisely because it is open-source.





Member since:
2005-07-06
It's been a long time since I read up on the CDDL/GPL incompatibility debacle, and I never really got much of a grasp on it in the first place, so could someone who has a better idea of the problem please explain it to me?
Also out of curiosity, is CDDL equally incompatible with with GPL v2 and v3?