I've bought and sold numerous domains with no written contract of any kind. Key is that both parties are clear as to what is expected from the other; to the best of my knowledge, domain names is not a type of asset where written contracts are required.
With that said, escrow.com may be the solution you're looking for - it has been for some other folks in a similar situation.
https://www.escrow.com/
The buyer will need to setup a free account there - once done, you're good to go
Ron
You could claim you're caching the data akin to Google's cache LOL!
Seriously, just because it's not clear who created the content, doesn't mean you can just copy it - most all content is *automatically* copyrighted - this applies to many countries, not just the U.S.
With that said, you may cite portions of such content - for the author use something like "unknown" or "anonymous".
Finally, copying content verbatim may be within fair use rights in some rare instances - fair use is a tricky legal area and for most all entities/uses, including non-profits, such wholesale copying is asking for trouble.
Ron