Clarify license.

rubygem-rack.spec

@@ -19,7 +19,8 @@ Version:        1.6.0
 Release:        1%{?dist}
 Group:          Development/Languages
 # lib/rack/backports/uri/* are taken from Ruby which is (Ruby or BSD)
-License:        MIT and (Ruby or BSD)
+# lib/rack/show{status,exceptions}.rb contains snippets from Django under BSD license.
+License:        MIT and (Ruby or BSD) and BSD
 URL:            http://rubyforge.org/projects/%{gem_name}/
 Source0:        http://gems.rubyforge.org/gems/%{gem_name}-%{version}.gem
 %if 0%{?fc20} || 0%{?el6} || 0%{?el7}