[Plugin: WP e-Commerce] How to get category from URL?

I’m using the WP e-Commerce plugin. I’ve a product, which is placed in two categories (taxonomy wpsc_product_category). Because of this, the product can be visited from two URLs:
http://bellabike.dk.linux11.curanetserver.dk/produkter/tbh_bella_2/hurtig-justerings-sadelbolt/
http://bellabike.dk.linux11.curanetserver.dk/produkter/tbh_bella_4/hurtig-justerings-sadelbolt/

I would like to change something on the product page depending on the category (like inserting a custom text). How can I, using PHP, get the category or slug provided in the URL?