No, RFC graphics is not based on Blue Marble.
In 2005 I borrowed its peaks and its tundra only, and did the rest on my own.
After 2 years of RFC, its author tried to revoke the permission to use that graphics, but I ignored his request as BTS was already shipping. For this reason too (other than the fact that I don't like it), I'm not using it. I'm improving the graphics anyway, thanks to another user.
EDIT: actually I can see that he radically changed the colours in 4.0. Now it's very good, but as I said, I have enough reasons to do it on my own anyway. Stay tuned, in the next patch I'll propose some new stuff