Today, I found this quote of Woody Guthrie himself on techdirt:
«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.»
Love the quote. Love Woody Guthrie. Best of all, love the irony!