This is by the same company that runs Second Life, which has heavily regulated in-game gambling, even citing the "Reasoned Legal Opinion" of the "Attorney General of Alaska" for why the things they allow are legal in 38 states (and D.C.)[1]

So we know for certain that it is not legal for most forms of gambling, only for games that are at least 51% skill-based.

[1] https://wiki.secondlife.com/wiki/Linden_Lab_Official:Second_...