FishCart v.3 permits additional information to be controlled by database content without regard to what the content actually is or does. This permits expansion in other ways as well. Additional shipping tools or other functionality can be implemented as modular extensions to the base FishCart. Such an architecture permits maintaining strict separation between the FishCart open source and the closed source of modular add-ons. Nothing in this architecture dictates that modular additions need be closed source; that can be determined on a case by case basis.

The v.U software has a PHP component and a Java component. PHP is not robust enough to fully implement the UPS interface requirements. Thus the PHP component prepares the service request and passes it to the Java component; the Java component requests the information from UPS servers and passes the results back to the PHP component for final display to the end user.

v.U PHP installs a number of new files and inserts data into several FishCart database files. It does not alter the FishCart source in any way. FishCart v.3 is required for v.U installation.

v.U PHP/JSP installs the same files and data as the PHP only version. In addition, a Java Server Page (JSP) and compiled JAR file are supplied for installation into the JSP running environment. The Sun JRE 1.4 environment is required to support the JSP component.