If so, I see two possible cases here:
1) He forced himself into her before she could even wake - a very aggressive thing to do to anyone whether or not they've consented. Then it's definitely rape without any doubt.
2) He cajoled her while she was half asleep and started having sex with her in a way that she would have consented to had he been wearing a condom.
If 2, the point where it becomes rape is when she realises he doesn't have a condom and yet he continues despite her protestations. If she never realised he didn't wear a condom, then it's not rape. It's an evil and possibly criminal thing to do, but it's not "forcing someone to have sex against their will".
For the record, I think either action makes Julian Assange a total asshole, and quite possibly someone who should go to jail. But unless he actually committed rape I don't see who it helps to call him a rapist.