When does a spiritual successor become copyright infringement?

The world of video game creation has unique challenges in spiritual successors or homage works. Some of these works defeat challenges of copyright infringement while others do not. For example, 2014 game TxK was sent a letter by Atari threatening action due to the similarities between TxK and Artari’s classic Tempest.

What is a spiritual successor?

A spiritual successor is a work that is not an explicit sequel to a previous work, but has notable similarities to a prior work, wanting to evoke similarities to the predecessor work. Spiritual successors, however, can face legal liability if they infringe on another’s copyright. Copyright infringement occurs when there is unauthorized use of copyrighted material, by one who does not own rights in the material. To prove a claim of infringement courts look for (1) ownership of a valid copyright and (2) copying of constituent elements of the work that are original (Feist Publications, Inc. v. Rural Telephone Service Company).

The creators of an original work are copyright owners, the U.S. Copyright Act allows copyright owners exclusive rights “to prepare derivative works based upon the copyrighted work,” which includes sequels to pre-existing works (17 U.S.C. § 106). Thus, authors of an original work, say the owners of the Tempest video game, have a right to also produce a derivative sequel to that work. Therefore, the first element of the infringement test is satisfied – there is a valid copyright to a sequel work.

For the second element, there needs to be evidence of copying. This can be done directly, through evidence that the third-party actually and intentionally copied the work. But more often, this can be proven through circumstantial evidence that the third-party (1) had access to the work and (2) there are probative similarities between the original and substantive work to support that it was copied. If a work was widely disseminated, like a popular video game or book, courts hold that there was a reasonable opportunity to observe the original work, and thus the third-party had access satisfying the first prong. Probative similarities help prove that actual copying occurred. These refer to similarities that would be difficult to prove happened just by coincidence, for example, the existence of common errors.

When two works are strikingly similar, a court can presume that the third-party had access. To be qualified as strikingly similar, the similarities between the two works must be such that the only way the successive work could have come about is by copying and not independent creation.

When does a spiritual successor become copyright infringement?

When comparing the original and homage work the question becomes – are the similarities between the two so pervasive that the successive work copied independently created elements?

In spiritual successor video games, for example, expressive elements could be copied from gameplay mechanics, characters, setting and story. The source code of the game could be copied directly, the character names and background, the nuanced setting, etc.

Spiritual successors have not been found to infringe when they do not copy elements from the proceeding work and have a different, transformative expression from the original work. The successive work must be its own independent creation that adds something original and substantive. For example, Yooka-Laylee is not a Banjo-Kazooie clone, it is a new game. But, fans of Banjo-Kazooie may feel nostalgic when they play the spritual successor – despite the fact that it is, in fact, an original creation.

TL;DR: Spiritual successors infringe on copyright when creators copy creative elements of an original work. Successive authors can, however, have their own works, if they distinguish themselves without copying and create something beyond an “unofficial sequel.”