See https://github.com/citation-style-language/utilities/wiki for information about the contents of this repo.
The CSL utilities in this repo are released under the MIT license. The main exception is "RNG2Schtrn.xsl", whose exact license status is unknown, although the author Eddie Robertsson offers the file for download at http://www.xml.com/pub/a/2004/02/11/relaxtron.html?page=5.