These icons come from the FatCow icon set:

  http://www.fatcow.com/free-icons

They are available under the Creative Commons Attribution 3.0 License:

  http://creativecommons.org/licenses/by/3.0/us/

Some icons have been adapted from the FatCow set for use in Phabricator:

  key_question.png      (from key_*.png)
  source/web.png        (from world.png)
  source/email.png      (from email.png)
  source/conduit.png    (from satellite_dish.png)
  source/mobile.png     (from phone.png)
  source/tablet.png     (from tablet.png)
  source/fax.png        (from fax.png)