Unity license questions

If I buy a Unity Indie + iPhone Basic license,
is there any limit on the numbers of installed machines or numbers of installed times?

e.g.

I installed it on one Mac, and then I wanna installed it on another Mac, Should I need to uninstalled it on the first Mac and revoke the license though internet connection or email?

Thanks!!

 

Thanks!!

If I need to use the 3rd machine later, what should I do to migrate/revoke the license?

 

Thanks!!