Understanding and interpreting open source licenses is not always an easy task. Open source licenses are essentially unilateral; if you use the software, you agree to the terms of the license. There is no protracted negotiation process during which to ruminate and refine terms as is often the case for custom-developed software.
Adding to the difficulty in understanding and interpreting open source licenses is the fact that the more troublesome compliance terms have yet to be litigated, most notably the derivative works question in regards to the GNU General Public License. However, that does not mean there is no guidance.
This white paper examines the three most common open source licenses – GPL v2, LGPL v2.1, and Apache v2 – covering everything from the background of each license to practical compliance tips and sticking points to be aware of.