Getting grubby with ZFS

More specifically, shouldn't a clearer distinction be made between the terms under which Oracle distributes the software (it obviously has to choose one of the available licences, I presume it is not legally possible for it to use several versions of the licence in one act of distribution) and the options they give the person they distribute the software too for further distribution? I assume they are distributing under GPLv2, but nothing stops them letting the people who get it from them redistributing under GPLv3 without it affecting Oracle in any way.

Similarly there have been complaints regarding VirtualBox that Oracle should be bound to the terms of the GPL and publish the sources to the closed source parts because they distribute it. However, my understanding is that Oracle doesn't distribute it under those terms (they own the copyrights and can do more or less what they want), but they do allow people who receive it to redistribute it under the GPL, minus the non-closed parts.