What I have now is a non-BB data plan with a non-BB device. Does this mean I will have to get a BIS plan once I start using the BB?

This is why I can't believe I am required to pay the 29.99 monthly charge, if I don't setup anything thru BIS: many other phones (non-BB devices) can use Gmail mobile or Yahoo mail mobile for free by using their respective download apps . How can BB/Sprint force a charge when that's possible? If indeed Gmail mobile works outside of BIS, how can they force you to pay that charge and go thru BIS?