MiniVend can share product databases, session files, and any other databases.
To make a mall, where all merchants submit orders through one clearing house, simply share the session file among all of the merchants. Any ordered items from any of the catalogs will show up in the same shopping basket.
There are some caveats. It will be a good idea to add a product attribute that holds the merchant number, to distinguish between possibly identical part numbers. This would also mean using the SeparateItems directive to place all orders on a separate line. MiniVend 3.x does this automatically, provided the databases are set up as separate files using the ProductFiles directive.
Pricing information will only come through if the merchants all share a product database, or at least share a pricing database. If the second is desired, you must build a pricing database that holds all merchant part numbers, ensuring no two are the same, and configure the PriceBreaks directive to start at quantity 1.
You can easily have some merchants who share a database and order point, while others operate completely independent catalogs -- all running from the same MiniVend server.