add a category view on the right side..

Can you not simply try the following? . . .

Navigate to /app/design/frontend/default/default/layout/catalog.xml

and change the position in which the category listing appears from "left" to "right"?

for example:

Code:

<reference name="left">
            <block type="catalog/navigation" name="catalog.leftnav" template="catalog/navigation/left_nav.phtml" />
</reference>

to

Code:

<reference name="right">
            <block type="catalog/navigation" name="catalog.rightnav" template="catalog/navigation/right_nav.phtml" />
</reference>

How can i add a category list on the right side?

in which page you want to display the category list ?

Ive been a user of joomlart but this template is by far the worst….
I saw that it was free… why is that?

Regarding JM Trex free download, yes we have recently made JM Trex available for Free. We will send you, as well as other Trex users, a coupon code which you can use to get another theme for free in replace of JM Trex. Stay tuned!