License Proliferation Categories
Here are the criteria used in the License Proliferation Report for placing licenses in the various groups:
Licenses that are popular and widely used or with strong communities
We used statistics obtained from public sources to determine which licenses are widely used. We believed that there were a few licenses that, while not the most popular, were widely used within their communities and that these also belonged in this group.
Special purpose licenses
Certain licensors, such as schools and the US government, have specialized concerns, such as specialized rules for government copyrights. Licenses that were identified as meeting a special need were placed in this group.
Licenses that are redundant with more popular licenses
Several licenses in this group are excellent licenses and have their own followings. The committee struggled with this group, but ultimately decided that if we were to attack the license proliferation problem, we had to prune licenses. Thus, licenses that were perceived as completely or partially redundant with existing licenses were placed in this group.
Licenses in this group are specific to their authors and cannot be reused by others. Many, but not all, of these licenses fall into the category of vanity licenses.
Licenses in this category have been superseded by newer versions. Licenses that have been voluntarily retired Self-defining category. No one should use these licenses going forward, although we assume that licensors may or may not choose to continue to use them.
These licenses do not fall neatly into any category.