gnu: licenses: Add NCSA license.

* guix/licenses.scm (ncsa): New variable.

guix/licenses.scm

@@ -41,6 +41,7 @@
             imlib2
             lgpl2.0 lgpl2.0+ lgpl2.1 lgpl2.1+ lgpl3 lgpl3+
             mpl1.1 mpl2.0
+            ncsa
             openldap2.8 openssl
             psfl public-domain
             qpl
@@ -249,6 +250,11 @@ which may be a file:// URI pointing the package's tree."
            "http://directory.fsf.org/wiki/License:MPLv2.0"
            "https://www.gnu.org/licenses/license-list#MPL-2.0"))
 
+(define ncsa
+  (license "NCSA/University of Illinois Open Source License"
+           "http://directory.fsf.org/wiki/License:IllinoisNCSA"
+           "https://www.gnu.org/licenses/license-list#NCSA"))
+
 (define openssl
   (license "OpenSSL"
            "http://directory.fsf.org/wiki/License:OpenSSL"