Free Icon Set “Softies”
Free Icon Set “Softies” is a free Icon design resource made by Dribbble user Kenny Sing. As far as I can tell, its license is GNU General Public License.
Helpful hint: Dribbble users are nice. If the license is unknown, it is usually because they forgot to mention it explicitly; not because they were being stingy. Ask nicely and they will probably allow you to use it.