Linux: The Grey Borders of the GPL

Linus Torvalds first released the Linux Kernel in September of 1991 under a very restrictive license requiring that the source code must always be available, and that no money could ever be made off of it. A few months later, he switched to theGPL, or GNU General Public License, the license that has been used for the Linux kernel source code ever since. A recent thread on thelkml discussed some of the grey areas of legality where it's not explicitly clear what the GPL allows. Alan Cox [interview] was one of many kernel developers to offer some insights:

"The boundary of the GPL is what is called a 'derivative work'. This is the basic concept in law used by copyright and essentially asks 'is this work created in such a way that it is based on the original work in some meaningful fashion'. Its a complex area of law and only a lawyer can give definitive answers."

"The simple 'application for Linux' case is clear. The simple 'kernel modification' case is also clear. In the middle is the vague area that is for lawyers."