That's how the Swedish court system works, he has been accused (with the higher level of confidence if I remember correctly) and won't get formally charged until it is taken up in court. The system is a bit different compared to for example USA.

He was taken into custody while the investigation was being finished up.

Ah yes, that's ringing a bell (I think from the whole Assange debacle). Makes the reporting in torrentfreak guilty of some rather dishonest spin doesn't it?