What is the latest version of Unity that runs on a PowerBook G4?

What is the latest version of Unity that runs on a PowerBook G4 and is it possible to get? If it is possible to download, where can I download it?

Unity 2.6.1. See here for download link: http://answers.unity3d.com/questions/25851/how-do-i-download-unity-2-x

@Eric5h5
does that version run 3d