If you want to get a true sense of the proliferation, you need to (mathematically, as in weighted average) project the top 100 projects from the Black Duck list, against the number of downloads (for a lack of a better measure of the extent of distribution) for each of those projects. Then take the top 100 downloads and project them on the licenses. From the two lists, get the top 10 or 20. You will soon see that a license proliferation is not a big issue, because to top 10 licenses as defined by Black Duck, Google, and Krugle cover most open source software. Furthermore, there are really only 3 families of licenses with GPL variants in one family, MPL/EPL and variants in another family, and BSD/MIT/Apache in another family. These 3 families plus public domain software cover 99% or more of open source code (I would bet). i.e. You don’t have to learn that much about licenses, and license proliferation is not as bad as some may think.