licenses: Add 'x11-style'.

* guix/licenses.scm (x11-style): New variable.

guix/licenses.scm

@@ -39,7 +39,7 @@ (define-module (guix licenses)
             psfl public-domain
             qpl
             vim
-            x11
+            x11 x11-style
             zlib
             fsf-free))
 
@@ -236,6 +236,16 @@ (define x11
            "http://directory.fsf.org/wiki/License:X11"
            "https://www.gnu.org/licenses/license-list#X11License"))
 
+(define* (x11-style uri #:optional (comment ""))
+  "Return an X11-style license, whose full text can be found at URI,
+which may be a file:// URI pointing the package's tree."
+  (license "X11-style"
+           uri
+           (string-append
+            "This is an X11-style, non-copyleft free software license.  "
+            "Check the URI for details.  "
+            comment)))
+
 (define zlib
   (license "Zlib"
            "http://www.gzip.org/zlib/zlib_license.html"