No, it doesn't depend on Mobile Kit Pro, you can set any skin as the mobile skin and it will use that skin for mobile devices. So for example you can use the UserAgent Plugin in Firefox to impersonate iPhone and you will see it uses the skin you specify as the mobile skin. The Mobile Kit Pro documentation explains how mojoPortal detects mobile devices.
So being able to set a mobile specific skin is just part of the solution,, you can try to implement your own more mobile friendly skin or you can buy Mobile Kit Pro and customize it.
The documentation also mentions a new control in mojoPortal that you can put both in your mobile skin and your normal skin (in layout.master) to allow mobile users to toggle between the mobile skin and the normal site view.
Hope that helps,