All shaderlab (http://www.shaderlab.com/) textures (by Randy 'ydnar' Reddig)
are subject to the following license:

  Usage and redistribution policy: Textures may be freely downloaded,
  modified, and used in free maps, mods or total conversions provided
  this copyright notice is left intact and a link to Shaderlab is
  provided in the credits or read-me file. Other non-commercial
  applications are considered on a case-by-case basis via e-mail.
  All other usage requires written permission. Bulk redistribution
  or archival of the textures in any medium, digital or
  otherwise (except mapping packages for mods) is prohibited.