From the publisher blurb:
This document contains the current systems reference document for the Worlds Without Number fantasy RPG. It is provided under a Creative Commons 0 waiver allowing downloaders to copy, modify, reproduce, or otherwise use it for both personal and commercial purposes. Later versions of this file may be released, but any released version may be used in perpetuity.
The contents of the SRD include the mechanics of the game and trivially-derived content such as weapon damage dice, spell and ability names, and other necessary material for reproduction and use. It does not include the specific setting of the game, the Latter Earth and its nations, individual NPCs, GM tool text, or other creative intellectual property not included in this document. Use of that IP is still reserved.