Wikipedia says [1]: 
&quot;License: Proprietary, with free download. (with patent claim)&quot;<p>[1] <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;F.lux" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;F.lux</a>