Hi Khurt,
this is exactly the reason why you are not able to "out-of-the-box" display your iCloud calendar in Google Calendar - and I agree, it does make sense to hide private data from the Google (or *name-your-search-engine*) crawlers.
Unfortunately I didn't have the time to test the solutions to that problem I have in mind, so I am just going to paste them here in case anyone wants to give it a shot:
1) Use the X-Robots-Tag http header
Place the following line next to the other header() calls in the php script:
header('X-Robots-Tag: noindex');
2) Use $_SERVER['HTTP_USER_AGENT'] to identify the user agent in the php script
Then decide for which useragent you *do* want to display content, and for which you may want to give an error message or simply a blank page.
List of search engine bots: http://antezeta.com/news/search-engine-crawlers
3) Similar to (2), use $_SERVER['REMOTE_HOST'] to find the source of the http request and block it accordingly
Maybe there is a more elegant solution than the ones mentioned, or maybe all possible solutions directly lead us to the problem where we are coming from (and thus Apple just lives with the fact that the calendar is not accessible from GCal). It's worth a try though 🙂
Cheers,
--
Thomas