As far as I know Linus holds the copyright to Linux.
While looking around in the kernel sources, I see that almost every file has it's own copyright holders. For example the file
module.c in the Linux kernel contains:
Copyright (C) 2002 Richard Henderson Copyright (C) 2001 Rusty Russell, 2002, 2010 Rusty
And the COPYING file in the root directory contains:
NOTE! This copyright does *not* cover user programs that use kernel services by normal system calls - this is merely considered normal use of the kernel, and does *not* fall under the heading of "derived work". Also note that the GPL below is copyrighted by the Free Software Foundation, but the instance of code that it refers to (the Linux kernel) is copyrighted by me and others who actually wrote it. Also note that the only valid version of the GPL as far as the kernel is concerned is _this_ particular version of the license (ie v2, not v2.2 or v3.x or whatever), unless explicitly otherwise stated. Linus Torvalds
So if Linus would want to change the license under which Linux is released, wouldn't he need the permission of all the copyright holders, which are probably 1000's of people?