Hi,
Yes the plugin can be modified to change the SQL query.
The current query look at the products on the user orders, to display the vendor's products, you will have to load the vendor of the user and look at the products for this specific vendor.
But because you will display the products and not the orders, the generated HTML content should be modified too.
The best at this moment will be to duplicate the plugin to have two distinct plugins for jomsocial.
At this moment you will be able to update HikaShop without loosing your modifications to the jomsocial integration plugin.
If you can gave us more details, we can see to put your request in the HikaMarket TODO list.
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.