I managed to fix it my own noobish way. I got in Notepad++ and opened default.php. This file was located in components\com_foxcontact\views\foxcontact\tmpl. The file your looking for is default.php
At line 60 there is the following: <a href="http://fox.ra.it" title="Joomla contact form" target="_blank">Powered by Foxcontacts</a>
I first tried removing the entire code, but that resulted in a 500 Internal Server Error when reloading the page, so I wisely put that back. Then what I did (I've been at this thing, reading through this topic and trying stuff all day) was just leave the space between
empty. And the link was gone. Its not the cleanest way of getting rid of it. But hey, it works.
This worked for me in Joomla 2.5.7.
Fox Contacts version 2.0.17
I completely agree with 2u3. Under the GNU/GPL license, the code is supposed to be completely opensource. People using this extension should be able to just choose if they want the link there or not. Thats what opensource is supposed to be. You are trying very hard to stop people from doing that, and actually asking money for removing it. What you are doing, is actually a violation of the GNU/GPL license, and I could take this to court if I wanted to, but thats just not worth my time.
Apart from that, this is a great extension, its very easy to use, just a bit hard to customize to your own needs
Actually, if it was easier to modify (manually or from within the Joomla backend) I would've payed money for it