Suggestion 1:

Caching is declared NOT redistribution -> Continue as is.

(especially no alteration of data performed!)

Suggestion 2:

Implement HTTP markup tag that states: Copyright data / Not to be Cached

(looks like HTTP 1.1 would do the job - when?)

Suggestion 3:

implement a reporting mechanism that lets caches send summarized access-statistics back to the original sources (via HTTP / ICP / Mail whatever fits) -> redistribution is overseeable

Suggestion 4:

"official" registered caches in THE hierarchy. Groups could be: Commercial, educational, experimental + their hierarchy level (1st, 2nd...)

Helpful pointers:

marvel.loc.gov/copyright/

www.eff.org/pub/CAF/law/ip-primer

FAQ: www.clari.net/brad/copymyths.html

www.4patent.com/copy1.htm