I personally believe that there is no need to release OpenSolaris uder GPLv2. you should know that CDDL is not the only license that is incompatible with GPLv2. APL2.0, MPL, EPL, GPLv3, AGPLv3 all these licenses are incompatible with GPLv2. however FSF has made it clear that if a software is released under a free software license (like CDDL) then it is legal to mix the software with GPLv3. »