I need a shopping cart like Americacart , but I don’t want to pay annual fees, what I want is to “own” the shopping cart., any suggestions ?

try www.theexchangeproject.org (I think they've moved but you'll get redirected from there)

Take a look at

http://www.vpasp.com

Very customizable shoppingcart .. and has support for 15+ payment gateways.

Here are two others you can look at
www.storefront.net
www.miva.com