Lately I’ve been taking a look at the various open source software licenses in an attempt to better understand the differences between them. Here is my five minute summary of the most popular licenses:
GNU Public License (GPL)
Requires that any project using a GPL-licensed component must also be made available under the GPL. Basically once you go GPL you can’t go back.
Lesser GNU Public License (LGPL)
Basically the same as the GPL except that if something uses software licensed as LGPL it also doesn’t need to be licensed the same. So if you write a program that uses an LGPL library, say a program with a GTK+ user interface, it doesn’t need to be licensed LGPL. This is useful for commercial applications that rely on open source technology.
v2 vs v3
There are a number of differences between version 2 and version 3 of the GPL and LGPL licenses. Version 3 attempts to clarify a number of issues in version 2 including how patents, DRM, etc. are handled but a number of developers don’t seem to like the differences so version 2 is still quite popular.
This license allows for almost anything as long as a copy of the license and copyright are included in any distribution of the code. It can be used in commercial software without issue.
Similar to the MIT, this license basically only requires that a copy of the license and copyright are included in any distribution of the code. The major difference between this and the MIT is that the BSD3 prohibits the use of the copyright holder’s name in any promotion of derivative work.
Apache is similar to the BSD license in that you have to provide a copy of the license in any derivative works. In addition there are a number of extra safeguards, such as patent grants, that set it apart from BSD.
Previously I was running KDE 4.3.3 on top of Fedora 11 (for the first experiment) and KDE 4.6.5 on top of Gentoo (for the second experiment).