An anonymous reader writes "When first made available in September of 1991, the Linux kernel source code was released under a very restrictive non-GPL license requiring that the source code must always be available, and that no money could be made off of it. Several months later Linus changed the copyright to the GPL, or GNU General Public License, under which the kernel source code has remained ever since. Thanks to the GPL, any source code derived from the Linux kernel source code must also be freely released under the GPL. This has led many to question the legality of 'binary only' kernel modules, for which no source code is released. Linux creator Linus Torvalds talks about this issue in a recent thread on the lkml."