It goes a little further than that in fact. The author has actively integrated fan-creations into the Log Horizon world. D.D.D. member Alakshmi, who makes a brief appearance in the anime, is originally from a fanfic called D.D.D. Diaries and much of the guild's history was drawn from the same fanfic. (the fanfic's in japanese, sadly making it relatively impenetrable to me).
D for Drakensis
You're only young once, but immaturity is forever.
D for Drakensis
You're only young once, but immaturity is forever.