The resource agent should contain a comment listing the resource agent author(s) and/or copyright holder(s), and stating the license that applies to the resource agent:

#
#   Resource Agent for managing foobar resources.
#
#   License:      GNU General Public License (GPL)
#   (c) 2008-2010 John Doe, Jane Roe,
#                 and Linux-HA contributors

When a resource agent refers to a license for which multiple versions exist, it is assumed that the current version applies.