ZFS.

[Alan Cox]

On Thu, Nov 17, 2005 at 09:20:00PM -0800, Toshio Kuratomi wrote:
> classified as a derivative work.  If it's classified as a derivative
> work then it's in violation of the GPL whether or not it's distributed
> in the kernel, right?  IANAL and I am very tired at the moment so my
> chain of reasoning here could be totally specious.

Basically for a derivative work you must meet all the requirements of all
the licenses simultaneously. 

eg if you combine a work that is 'non commercial use' and a work that is
licensed 'for stage performance only' you end up with a work that is licensed
for non commercial stage performance only.