Can a Spinning Axe be used on units other than Draven?

Yes, a Spinning Axe can be used on units other than Draven.

According to the card's text, the [Equip] ability allows you to attach it to "a unit you control." While the card is associated with Draven (as indicated by its tags and signature status), there is no restriction in the card's rules text that limits its use exclusively to him. You may attach it to any unit you control by paying the [Equip] cost.