To avoid any confusion regarding the status of applications running on top of the Linux kernel, Linus Torvalds added the following preamble to the kernel's license:
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_ license (ie v2), unless explicitly otherwise stated. Linus Torvalds