Sidious had to have known Juyo in order to train Maul in that form. It is possible that Sidious knows a little bit of all forms, which would make sense. His style is ambigious and often mimics the stances of various lightsaber forms, predominantly Ataru and aggressive Dark Side attacks. Thus, I believe, it is a combination of Ataru and Juyo.
Originally posted by Shadow x 20Nah.. He couldn't have known Vaapad..
It's possible for Sidious to know Vaapad. I mean how long has Mace developed it? Prior to The Phantom Meance? If anything that could give Sidious over a decade to learn it but I strongly doubt he did. I would say his form was like that of Yoda's with some added twists.
I think it's important to realize that saber forms aren't just ways of using your glowstick; they're fighting philosophies and approaches to combat. Sidious may have used things such as Ataru-esque flips or spins, or even Makashi like stabs, but his overall approach was closest to Juyo, in which he is unpredictable and aggressive, almost amateur looking in his approach.
Well I just watched his fights with windu and yoda again. And I think that he uses a blend of makashi,juyo,and ataru, but who knows, He did do that spinning manuevre and take out two jedi, then he seemed more "robotic" while fighting mace in that hall way like area, but in the open before the window broke he flipped again and performed what I thought was makashi-like thrusts and stabs.....before he got kicked in the face.