Add non-commercial licenses

[EwoutH]

Currently all licenses allow commercial use. While in many cases that’s fine, there is a use case in non-commercial licenses, and it would be nice to have a few options listed.

One use case would be making source code available for individuals and researchers, but don’t allow commercial use by default. In some cases this might be combined with more permissive licensing on case/contract basis.

Having a non-commercial license is in many cases more free than “No license” situation.

Two potential options to add are:

• CC BY-NC 4.0
• The Commons Clause