Plone Theme Licensing Policy
These recommendations cover the distribution of theme packages for use with Plone. Themes that are not distributed do not, in general, fall under the licensing restrictions discussed here. Note that the term "package" here is used in the sense of a bundle of functionality, and not in the narrow sense of a Python package.
It is the opinion of the Plone Foundation that Plone theme packages containing Python or page-template components that import functionality from Plone's GPL components should be regarded as derivative works and, when distributed, be licensed under the same terms as Plone itself.
Any Plone theme package, whatever the license, may be listed in the products section of Plone.org. Plone theme packages that are uploaded to Plone.org for distribution must be licensed under the GPL, Creative Commons, or similar open-source licenses. Those wishing to use non-open-source licensing terms should make other arrangements for distribution. All packages listed on Plone.org should specify their licensing terms.
Copyright and licensing law varies over time and from jurisdiction to jurisdiction. The recommendations here are meant to express the opinions of the Plone Foundation, and should not be regarded as legal advice.
Adopted by the Board of Directors of the Plone Foundation, July 14, 2011.