As of January 20, 2015, Google Earth Pro is free for anyone to download and install. Even though use of Google Earth Pro still requires a license key, you may use your email address, and the key GEPFREE to sign in.
Google Earth Engine brings together the world's satellite imagery — trillions of scientific measurements dating back almost 40 years — and makes it available online with tools for scientists, independent researchers, and nations to mine this massive warehouse of data to detect changes, map trends
Google Maps API for Business is to visualize location based data or engage your customers with embedded interactive maps. There are important differences between Google Maps API for Business and the Free Maps APIs.