Amazon S3 / WebDAV proxy updated 
I took the liberty to check out
my old code and work on it to finally fix some of the problems. It now correctly uses the last-modified time and the cache handling as well as lazy download from S3 is implemented. To really work with the server it will need better cache handling. After many tests the basic and copymove finally run through repeatedly without failure.
Still a long way to go.
Update: (2009-01-28) In the meantime I implemented the property handling which only fails for some strange UTF-8 property values. Now the litmus test runs 99% through. Using MacOS X Finder to test looks promising.