I'm not sure about the details, but to write a linux kernel module you must include some .h files under the GPL license. You really have to include it because linux ABI is intentionally not stable exactly to prevent proprietary abuse. So, AFAIK, every functional linux kernel driver must be released under the GPL.
The point is: if you want to include a GPL licensed header, your code must comply with its license. Your opinion on the GPL is an entirely different matter.
