In most cases it should be clear whether your usage of the AJAX APIs complies with the posted Terms of Use. However, if you are still unclear, and have a strong vested interest in resolving any confusion, it is best to consult a lawyer who can give professional legal advice on this. Google engineers can only offer technical advice in the forum and are not qualified to offer legal advice.

The Developer Guide can be found at http://code.google.com/apis/ajaxfeeds/documentation/.

The Google AJAX Feed API is a JavaScript API that enables developers to easily use data from public feeds in their AJAX applications. The AJAX Feed API comes with Google hosted server-side technology to proxy and parse feeds from any source, and exposes the data through a JavaScript API which can be used purely from a client browser. JavaScript developers now have access to any feed data from any host!

The AJAX Feed API can be used entirely in JavaScript to extract public feed data. Once in JavaScript, feed data from one or multiple sources can be mashed up with other JavaScript APIs such as the Google Maps API to provide innovative ways to view the feed data.

Google.com serves as a proxy to the outside feeds, so your client code only communicates with Google servers.

The AJAX Feed API supports the following feed formats: Atom 1.0, Atom 0.3, RSS 2.0, RSS 1.0, RSS 0.94, RSS 0.93, RSS 0.92, RSS 0.91, RSS 0.9.

The AJAX Feed API has the ability to return feed data in JSON, XML or a combination of both. The JSON format returns an abbreviated, canonicalized result format based on the original feed. The XML format returns the actual XML content from the feed.

The unified feed result elements are: title, link, description, author and a list of entries[ ]. The entries[ ] list has the following elements: title, link, content, contentSnippet, publishDate, and categories.

You can access the elements in the returned XML document by using XML DOM functions like getElementsByTagNameNS(). The AJAX Feed API includes a cross browser implementation of this function called google.feeds.getElementsByTagNameNS(node, ns, localName).

Yes, you can use the combined JSON/XML result format (MIXED_FORMAT). This format has the benefit of both the simplified, canonicalized feed format but with the ability to access all the XML elements returned from the feed.

The Google AJAX Feed API uses the same feed caching and sharing mechanism as Google Reader, which means that feed data from the AJAX Feed API may not be completely fresh, particularly for frequently updated feeds. The Google feed crawler ("Feedfetcher") retrieves feeds from most sites approximately once per hour. Some frequently updated sites may be refreshed more often.

See the Google Webmaster Tools Help Center for details on Feedfetcher.