Game creators lay down the rules for making your own Servant-inspired creations.
What's permissible and what's verboten in the world of anime fan works is slowly getting less blurry. Rights holders are coming forward swiftly to shut down doujin creations, with Love Live! being one of the most notable to lay down a zero-tolerance policy. Often, the statements given are so broad and generalized that it's hard to tell how "zero" the zero-tolerance is.
Fortunately, Fate/Grand Order fans don't have that issue. Type-Moon has released their guidelines for doujin/derivative works, both with regards to what can be made and what can be sold.
According to the company's guidelines, doujin works may not include art or animation lifted directly from the game, branding or logos either lifted from the game or designed to be evocative thereof, game scenarios, or music. Characters and their likenesses may be reproduced, however, and reference can be made to official game scenarios provided the main scenario is an original fan creation. Additionally, no cover art from the Fate/ franchise may be lifted for the purposes of doujin project covers.
As for sales, doujin creations may only be distributed or sold as clearly fan-made items as part of doujin events/tables, and may not be distributed commercially.
3D representations of the characters, such as model kits, may not be created or distributed.
Type-Moon has also promised to keep their rules updated, should the standards change at any point.
Kara Dennison is responsible for multiple webcomics, blogs and runs interviews for (Re)Generation Who and PotterVerse, and is half the creative team behind the OEL light novel series Owl's Flower. She blogs at karadennison.com and tweets @RubyCosmos. Her latest story can be found in Ride the Star Wind, available now from Broken Eye Books.