This is what LINK is designed for: <LINK REL="copyright" HREF="...">. If
you need additional structure for the data you can define a standard
data format and assign it a MIME type (e.g., application/x-copyright).
Servers can then automatically detect client support for that format via
the HTTP Accept: attributes.
Also, HTML LINK attributes can be exported to the HTTP header using WWW-Link:
--sanders