All the materials you find on the CTS website are covered a Creative Commons Attribution Share-Alike licence, version 2.0 for the UK (usually abbreviated to CC BY-SA and visualized as the icon below). This means that you are free to copy, distribute, display, and perform the work and make derivative works from it. (We'd appreciate a pair of free tickets if you manage to perform anything you find here.) But only on the understanding that you must give credit to the original author (either CTS, or whoever is credited on a particular page) and that if you alter, transform, or build upon this work, you may distribute the resulting work only under a licence identical to this one. Woody Guthrie had the right idea:
"This song is Copyrighted in U.S., under Seal of Copyright #154085, for a period of 28 years, and anybody caught singin' it without our permission, will be mighty good friends of ourn, cause we don't give a dern. Publish it. Write it. Sing it. Swing to it. Yodel it. We wrote it, that’s all we wanted to do."