The icons are free to use for personal and commercial use. 

But required to backlink to WHCompare.com somewhere on the page where it is used when possible,
or on another page when not possible, or in the code when possible, or without the link at all when not possible.

You are alse free to share the icons for download on your site if you add a link to WHCompare.com
and credits that site as the owner of the icons.

The icons was commissioned by WHCompare.com which is a web hosting review and comparison site.

You can find more details about them at this page: https://whcompare.com/blog/icons/