The GPL is not viral

I was listening to a recording of Chris Messina talking about building infrastructure for the open source community at BarCamp Dallas; in the middle of the recording, a discussion started about the new version of the GNU General Public License.

Someone in the crowd claims the GPL is a “viral” license. This is a claim that has been repeated for years; unfortunately, it’s a ridiculous metaphor. The GPL says that if you download code under the GPL, change the source code, and release a new version, you have to release your changes to the source as well.

A virus, on the other hand is something that infects you, despite your best efforts to avoid it. The measles virus, for example, is passed through airborne particles. Nobody gets the measles on purpose.

The GPL may seem viral—if you include GPL’d code in your proprietary program, then you have to release your entire program under the GPL. The misleading part is that while you might contract the measles despite your best efforts to avoid it, it is unreasonable to say that you will inadvertently introduce GPL code into your program.

“Oh, I accidentally went to Sourceforge, downloaded a tarball, opened it, and copied code with the exact functionality I was looking for into the correct part of my program! Oh no! Help! I’m infected with the GPL virus!”