Google Maps: Map Type (Roadmap, Terrain)

I just came across the following web site and noticed they had 2 map types I'm not certain on how to activitate from the Google Maps JavaScript API.

ht开发者_开发知识库tp://www.maps-for-free.com/index.html

It's the "Relief" and "OSM" Map Type as found on the link above.

Any ideas what the API call is to display "Relief" and "OSM" from a Google Map?

This is not a standard Google Maps API map, it is a layer added by the website. There are relief layers out there you can download and implement yourself actually the website you showed is offering this service.

Look at the top of the link you provided, you will find Tutorial (Mashup-Example) - Downloads

Open these links and you will see how stuff works.