It's not entirely clear with the GPLv2 that that's the case. The FSF claims that because modules are loading into the address space of the kernel that makes them an integrated part of a single program and not mere aggregation, and are therefore covered by the GPLv2's restrictions as a derivative work.
It should be noted, however, that this is merely the FSF's opinion, and this has never been definitively legally established.
The GPLv3 was designed to, inter alia, eliminate such ambiguities, but added so much complexity it never really caught on outside the GNU project.