This should answer your question -
You can sell games but you need to keep the OSM data open. Same applies to freeware I would assume. 
Keep in mind that OSM data does not mean 3D Models, 3D Roads or Terrains it just means the data used by OSM to generate such things.
That is how i translate it. I am also not a lawyer.
Further expanding on it - I have dug into the license and here is what is said about commerical stuff
That is from Section 3.0
Edit:
That said - The folks over at BitBunch are using OSM and SRTM data extensively in their custom engine according to their blog - http://bitbunch.eu/dev-blog-5-world-enough/