Once you’ve signed up on the Rhino OSX site, the download link appears:
As for mouse, I’ve tried the Magic Mouse on my retina MacBook Pro. In Rhino OSX, it works OK. I love the fact that it operates over Bluetooth thus saving a USB port from being occupied. Also found it pretty slick that it can bring the system out of sleep. Problem is, I setup the notebook to dual-boot into Windows7 (T-Splines) and that’s where the Magic Mouse lost its luster. Apple’s Win7 drivers for the Magic Mouse would cause right-click operations to only work half the time. Right-clicking is crucial to rotating around an object, but MOST of the time, what I got with the Magic Mouse was a mis-translated middle-mouse-click giving me the pop-up toolbar. Stylistic coolness aside, this Rhino user needed his discreete mouse buttons.
I’ve been using the Microsoft Sculpt Touch Mouse for nearly a year now. It’s been working well booting into Win7 or OSX. It’s Bluetooth, so again connects with the MacBooks. The typical mechanical scroll wheel (aka: Food Trap) is replaced by a solid-state touch-sensitive strip. I don’t know if iMacs include Bluetooth, but if it’s on the checklist, I can vouch for the Microsoft Sculpt Touch.
Logitech recently announced their Magic-Mouse contendor, the Touch Mouse T631. I’d expect it to work comparably in OSX. The question is whether it’s better than the Magic Mouse in Win7 (working in Rhino 5).