GNU Modula-2 is free software, the compiler is held under the GPL v3 http://www.gnu.org/licenses/gpl.txt, its libraries (pim, iso and Logitech compatible) are under the GPL v3 with the GCC runtime library exception clause.
Under Section 7 of GPL version 3, you are granted additional permissions described in the GCC Runtime Library Exception, version 3.1, as published by the Free Software Foundation.
You should have received a copy of the GNU General Public License and a copy of the GCC Runtime Library Exception along with this program; see the files COPYING3 and COPYING.RUNTIME respectively. If not, see <http://www.gnu.org/licenses/>.
More information on how these licences work is available http://www.gnu.org/licenses/licenses.html on the GNU web site.