There are apparently some issues with the UIWebView manifest and cache manifest files.
Html5 cache manifest in UIWebView?
There are answers to similar questions on the Google PhoneGap group mailing list, but this does not mean that it cannot be done on PhoneGap at all.
Note. I also saw someone answer your question on the google groups mailing list, simply suggesting that in the example you gave, they cache files that you could just include in the PhoneGap application. Although this will work if the files were disabled, if they ever needed to be updated, it would be nice, not so much "cached" as "static".
Perhaps if that were the case, could you use the FileGap File api to get updated versions of files and store them locally (overwrite the old one)?
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