The officials and the employees of the Department of Agriculture engaged in the activities described in section
450b of this title and paid in whole or in part out of funds contributed as provided therein, and the persons, corporations, or associations making contributions as therein provided, shall not be subject to the provisions of section
209 of title
18; nor shall any official or employee engaged in the cooperative activities of the Forest Service, or the persons, corporations, or associations contributing to such activities be subject to such section.