Those seem like pretty circumstantial allegations to me, but we'll have to see what the courts say. It's basically their word against his.
If a man is not using a condom it's your responsibility to know that before he is penetrating you, just as much as it's his responsibility to be wearing one. The allegation that he had sex with one of them while she was asleep and didn't use a condom seems highly unlikely to me. Like she wouldn't wake up? If she did and let him keep going, again it's her own fault for not turning around and asking the simple condom question.
I'm not the kind of person who blames rape victims but calling this rape is a stretch, and you can tell that Sweden is really trying to milk this obscure law in order to get Assange into custody.