I don't think you want to find out that a driver is derived from
the OS
it is written for, or you'll find all kinds of lawsuits crawling out of
the closet about code included in linux that was originally written
under some other OS.
Being written under some other OS is not the same as being derived from
(any more than being compatible with is derived from). Derivative works
are a much more complex idea than that which is one reason there is a
lack of certainty on the issue.
Alan