You can't, in general, do that. The kernel developers and the FSF have always claimed that loadable modules (like the exFat driver) are "derived works", which

You can't, in general, do that. The kernel developers and the FSF have always claimed that loadable modules (like the exFat driver) are "derived works", which has a specific meaning in copyright law. In particular, the GPL very clearly says that derived works must be re-licensed under GPL. The vendors claim that "derived works" doesn't include linked code, or plug-in patterns. They say that they aren't really releasing their own kernel, just releasing the stock kernel with a bunch of proprietary applications on top, along with their proprietary kernel module. Like that guy said, it's a gray area.