yes it dual format. I only installed the window version, but on 2 of my computers. Also did this for Adobe creative suite cs5.5e (with photoshop 5.5e). I use the same user logging info, adobe hasn't bug me at all, so I think they expected people to install multiple copies in their home.
Sorry I need to clarify. Even though it come with both window and MAc, I heard you have to stick to one platform. But I guess adobe won't let you do dual format. You can install the same copy on multiple computers either all window or mac.