There were exemptions for fantasy sports made under the Unlawful Internet Gaming Enforcement Act. Basically, it's legal to 'gamble' on fantasy sports given the following conditions:

1. The prizes offered are established ahead of time (fixed prize pool, most sites implement this by capping the number of entries - and covering any overlay if not enough people enter)

2. The scoring is based on statistical results in multiple-real world games (none of the DFS sites allow you to 'bet' on a single games - the players must come from a pool of at least two NFL games)

3. Can't make "traditional bets" (spread, over/under)

(And less revelant to most people, you can't play fantasy for money if you are an member of the team - i.e. athletes can't 'bet' on themselves)

It's legal because no major industry has turned their lobbying efforts on outlawing it yet. There's no clear philosophical line between gambling and, say, investing.. there's just (decreasingly) moral crusaders and (increasingly) interests who profit from keeping things illegal outside of their personal holdings.

They are legal because the courts and legislation(such as the UIGEA) have deemed them to be legal.

I don't understand what seems to be a distinction between daily games and season-long leagues. Season-long outcomes are affected by injuries and other random factors as well(just ask anyone who drafted Adrian Peterson with their first pick this year).

It is certainly gambling, but it's explicitly legal under certain conditions per the UIGEA. And there is definitely a skill component as well.

Not trying to be snarky, but I never understood how the stock market works (it seems just as random).

In fact, the article has a paragraph where one player is offended that he might look like a gambler and is compared to a .. stock market investor? Trying to set fantasy sports apart from gambling didn't work for me that way..