Dave Viner's Weblog

Open Source Licensing

Someday someone should write up a comparison of the open source licenses. I know very little about it, but I know that I don't know the precise differences, and since I'm not a lawyer, it's unlikely a read-through of the license texts will reveal those differences to me.

I tend to think of myself as a smart guy, but I still don't get all the little differences. For example, I know that the GPL is "viral", in that it attacts itself to other programs or libraries with which it is linked. I also know that the GPL is the most radical license.

But, what's the difference between LGPL and MPL? or MPL and ASLv2? or ASLv2 and BSD? And what does it mean when someone says "its in the public domain"?

And what does it mean when a piece of software is released under multiple licenses? Does that mean that the user of the software chooses the license? or that the user must abide by all restrictions of all the licenses?

If you think there aren't that many licenses, check out Open Source Initiative's list of licenses that count as "open source". Although the OSI has lots of good info on these licenses, I'm amazed that there isn't a "Beginner's Guide to Open Source Licenses".

I have found this book on Amazon, but it's humorously not available under any open source license.