These icons are from the Silk Icon set by Mark James, available at
http://www.famfamfam.com/lab/icons/silk/. They're made available under a
Creative Commons Attribution 2.5 License, which basically means you can use
the icons however you like (including modifying and redistributing them) so
long as you attribute them to Mark as well.

We've added to his set with a few of our own at 48x48 which can be used freely.
The 48x48 icons are (unlike the 16x16 icons) not exhaustive, and there are a
number of 16x16 icons that have no 48x48 counterpart. As of now, those are:

page_white_excel, page_white_film, page_white_powerpoint, page_white_word,
page_white_sound, page_white_compressed

There are, however, icons in the 48x48 set that can be substituted for these.
