kaled - 11:43 am on Dec 16, 2009 (gmt 0)

If you use several such products, create a "credits" page with a link to each product and a link to each license (stored on your server).

For any freeware product, whether open source or not, that should be sufficient provided the credits page can be easily found. I would also suggest that you do not use nofollow when linking out.

Kaled.