Below is some info from their Frequently Asked Questions:
1. Are these icons really free?
Yes, they are free as long as you stick to the rules in the Read-me / License Agreement. Also, in some cases you may need to notify the artists about using the icons and sometimes you need to give credit to them. You can see these restrictions in the pack archive or right under the download section.
2. Can I get permission to use certain icons other purposes that aren't allowed by the license?
You need to get permission from the author that created the icons. Iconspedia is only hosting the icons.
So there you have it. You need to ask the Author for permission. Iconspedia
only acts as the host.
Hope that helps.
"Wiz"