No. Both of the products are independent from each and has different purpose.

jStore is a shopping cart which only allow 1 store seller.

jMarket is a multi-vendor shopping cart where many different vendors selling products in one single storefront.

Actually jMarket has been built using jStore as a foundation, which means jMarket has all the capability of jStore as well. Even better both products share the same exact views and tables.

If you install both products in the same website, they are automatically in sync that you will not notice the difference and it does not duplicate any data. Joobi products are designed to work with each other, not againts each other.