Board Thread:Naruto Discussions/@comment-30168130-20161009021213/@comment-1872728-20161009123307

Elveonora wrote: But Orochimaru was said to have Senjutsu but isn't known to use Sage Mode, Sage Transformation or Curse Mark, so how does that work? To my understanding, he can only use senjutsu through a person that uses Curse Mark Transformation. The Curse Mark contains Orochimaru's Chakra, and also the ability to absorb Natural Energy (thanks to Jugo), which creates "Orochimaru's Sage Chakra", which is then traded with the user's Chakra for the user to utilise senjutsu.

So whoever uses Curse Mark Transformation, they're actually using Orochimaru's Sage Chakra instead of their own Sage Chakra, so technically it's Orochimaru that's using those senjutsu. Something like that.