The rules are only available in the box. Flying Frog has previously stated (and I agree) that much of the content of the expansion is found in the rulebook itself. For some games, releasing the rulebook makes sense. But in this case, I think leaving it offline is a good thing (especially the dots system). I'm afraid you'll have to purchase SotF if you want the extra stuff--and believe me, it's well worth the money.

I'd be willing to bet there's a fair number of people who, if given that specific rulebook, won't bother to buy the expansion. Much of Survival of the Fittest's content is found there--not in the tokens and scenarios with which it comes. This isn't an expansion where you can read the rulebook but not have access to the stuff inside. And if you want a PDF, I don't see why you can't have a download code inside that gives you a copy.

Honestly, I want to read rulebooks most of the time before purchasing a game. In limited circumstances, however, not having one freely available is better for sales than the alternative.

I wouldn't mind if they had some method to only give it to those who own it. Send in the proof or purchase or some sort of thing like that. But dammit I want my electronic copy. So much easier to figure out rules with a search function.