Sun could have written the CDDL to be GPL-compatible yet they chose not to and they generally refused to explain why. I suspect that they did not want to see OpenSolaris become an "organ donor" for Linux but they also didn't want to appear weak by saying so in public.

The closest I can find is where Simon Phipps said "to be GPL compatible you actually have to be willing to have your license discarded and replaced with the GPL. It's more a Borg-like assimilation than compatibility, in my view, and pretty undesirable as it results in future code enrichment being accumulated in some other code commons." https://web.archive.org/web/20050420234857/http://blogs.sun....