It's easy enough to obtain a new license id (quick, automated process)
and make a little patch (the license numbers are declared at the top of
weather.h).
The only thing I'm not sure about is legal ramifications, though it
looks like TWCi has had the same license since 2008.
Index: xfce4-weather-plugin-0.7.4/panel-plugin/weather.h
===================================================================
--- xfce4-weather-plugin-0.7.4.orig/panel-plugin/weather.h 2011-02-02 15:31:29.000000000 -0500
+++ xfce4-weather-plugin-0.7.4/panel-plugin/weather.h 2011-11-05 21:04:15.214103897 -0400
@@ -21,8 +21,8 @@
#include <libxfce4panel/libxfce4panel.h>
#include <libxfce4util/libxfce4util.h>
#define PLUGIN_WEBSITE "http://goodies.xfce.org/projects/panel-plugins/xfce4-weather-plugin";
-#define PARTNER_ID "1121946239"
-#define LICENSE_KEY "3c4cd39ee5dec84f"
+#define PARTNER_ID "1287437847"
+#define LICENSE_KEY "f5d0d6461b98f194"
G_BEGIN_DECLS
