XML : Google KML Schema License - kml22gx.xsd

Context:

Running continuous integration builds, it's nice to not rely on HTTP queries for a variety of reasons. We are manually parsing some data out of KML files, and as a first smoke test we're validating them against the KML schema. Presently we're using ogckml22.xsd, but we'd like to add support for Google's extensions, as we primarily use Google Maps/Google Earth. We downloaded the old schema and use it locally for KML validations.

Google Earth appears to produce KMLs with the following namespaces:

  <kml xmlns="http://www.opengis.net/kml/2.2"   xmlns:gx="http://www.google.com/kml/ext/2.2"   xmlns:kml="http://www.opengis.net/kml/2.2"   xmlns:atom="http://www.w3.org/2005/Atom">    

The http://www.google.com/kml/ext/2.2 is Google's own, and begins with this notice:

<!-- Copyright 2010. Google, Inc. All rights reserved. -->

The ancient Google Groups discussion here manages to not answer the question, but is the only resource I've found that directly addresses this.

tl;dr: What is the license for kml22gx.xsd? Can I legally download it and bundle it in an application/use it locally?