In many ways, this is the most important factor (at least, according to the courts).I’ve covered multiple aspects of Fair Use in other posts in this series, from an overview to the first, second and third factors. In this last post, I will cover the fourth and final factor that courts use when analyzing whether something is a Fair Use:
The Effect upon the Plaintiff’s Potential Market:
The last part of a Fair Use analysis involves looking at the effect that the infringing use will have on the potential market for the copyrighted work. In many ways, this is the most important factor (at least, according to the courts).
What counts?
Only the parts that are actually copyrightable count toward this analysis. If there is factual or functional information that isn’t protectable, the use of that info won’t be taken into account when looking at this fourth factor. 
The danger of circularity:
One issue with the fourth factor is the supposition that there is always another “potential” market for the copyrighted material. Therefore, any use by an infringer in another market is affecting the value of that material in that potential market. The Supreme Court limited this effect in Campbell v. Acuff-Rose Music, Inc., a case revolving around 2 Live Crew’s parody of Roy Orbison’s “Pretty Woman.” The Court analyzed this fourth factor by looking at the effect of the parody on Orbison’s normal (non-parody, non-rap) market for the song.
What evidence is used?
Since Fair Use is an affirmative defense, the burden of proving this factor is on the infringer.Since Fair Use is an affirmative defense, the burden of proving this factor is on the infringer. In the absence of any evidence or when the evidence is inconclusive, it seems that this factor will weigh toward the copyright owner. The actual evidence used will usually be speculative, since it is hard to prove one way or another what the effect on a potential market will be. Some suggest that customer surveys or other data could be shown as evidence, though surveys can be constructed in such a way that they prove any point. It is up to a court to decide if the evidence presented in persuasive. That wraps up our look at the nebulous concept of Fair Use. I will be collecting these posts into an eBook shortly, along with more analysis, specific case studies and excerpts from some seminal Fair Use case law. Just sign up below to get that sent as soon as it’s ready, along with my “5 Legal Moves Every Game Developer Should Make” eBook, my trademark branding and copyright checklists, as well as any future goodies that I come up with! And in the meantime, if you need a game lawyer, don’t hesitate to contact one for a free consultation. photo credit: Justin in SD and josef.stuefer via photopin cc
