Surely if they can find one part of the Linux kernel that the FSF has copyright to, then that opens the floodgates, and the full (legal) weight and force of the FSF can stand behind this? So so long as they have one part, they can fight this.
The FSF rarely engage in enforcement action themselves, even on works they hold copyright on. The Linux kernel has probably been more actively enforced than any GNU project, with the possible exception of gcc.
