Yes, you can change it in the code:
In wpc-product.php file located in wp-content/plugins/products/ find line 126 where it reads:
'rewrite' => array ('slug' => 'wpccategories', 'with_front' => false),
wpcategories in the above line with the name you want to use for your category slug.
Now find this in line 24:
'rewrite' => array ("slug" => "wpcproduct ')
wpcproduct with the name you want to use for the product slug.
Names in line 126 and line 24 must be different.
Then, just resave your site permalinks via Settings > Permalinks *this bit is important.
See http://wordpress.org/support/topic/changing-base-slug?replies=7 and http://wordpress.org/support/topic/product-urls?replies=13 for more extended discussion on this topic. Thanks