A dokuwiki render plugin that renders a user defined info message to the top of pages in user defined namespaces.
You can see the plugin in action on this page (yellow box).
You can get a zip file here: https://github.com/timbk/dokuwiki-disclaimer/zipball/master
This link also works for manual installation via the web interface.
The info box text is directly used from the config value. You can put arbitrary HTML there. As this field is only editable by admins this should not be a real issue and more of a feature. Use at your own risk, I give no guarantees for anything. Enjoy!