Interestingly, I found a message from Linus on a mailing list that says that he interprets kernel modules as not necessarily _having_ to be GPL'd...

Not quite. Linus grants an exception from the GPL for kernel modules that follow the standard module interface. In other words, the kernel is licensed under a modified version of the GPL. That's a little bit iffy, since it doesn't say so anywhere in the kernel sources (I think), and there's a lot of code in there that's not copyrighted by Linus and simply says "licensed under the GPL".

Borislav