Disclaimer: This is not legal advice.
I was trying to understand what is considered as "fair use" and what isn't, when it comes to the use of movie screenshots in non-profitable blog posts / personal online diaries. However it seems there's no clear definition for fair use.
According to the Fair Use page on the Stanford Library website,
"In its most general sense, a fair use is any copying of copyrighted material done for a limited and “transformative” purpose, such as to comment upon, criticize, or parody a copyrighted work. Such uses can be done without permission from the copyright owner."
It says it's legal to copy a copyrighted material without permission, if it's used for a "transformative" purpose. However, the definition of "transformative" is again (maybe intentially made) unclear...
"So what is a “transformative” use? If this definition seems ambiguous or vague, be aware that millions of dollars in legal fees have been spent attempting to define what qualifies as a fair use. There are no hard-and-fast rules, only general guidelines and varied court decisions, because the judges and lawmakers who created the fair use exception did not want to limit its definition. Like free speech, they wanted it to have an expansive meaning that could be open to interpretation."
It basically says it's hard to balance between copyright protection v.s. the need to facilitate creativity inspired by existing works. Therefore, a legal grey area is left as the middle ground.
A Real World Case
The decade-old lawsuit between Oracle and Google is a good illustration for the practical interpretation of fair use.
According to the file released by the US Supreme Court, Oracle sues Google for copying 10k+ lines of Java SE codes to build Android Java APIs. In April 2021, the Supreme Court finally confirmed that Google's behavior is considered fair use, primarily for the following 4 reasons:
1) The nature of the copyrighted work: "The nature of the work at issue favors fair use". Since the value of the copied API codes are closely bounded with the "uncopyrightable idea" of API and the programmer community that uses it, and is not something like an algorithm that actually performs a task, Google's behavior is "unlikely to undermine the general copyright protection that Congress provided for computer programs".
2) The purpose and character of the use: "Google’s purpose was to create a different task-related system for a different computing environment" and "copied only what was needed". Therefore, Google's behavior “adds something new, with a further purpose or different character” and hence is considered to be "transformative".
3) The amount and substantiality of the portion used in relation to the copyrighted work as a whole: "Google copied approximately 11,500 lines of declaring code from the API, which amounts to virtually all the declaring code needed to call up hundreds of different tasks. Those 11,500 lines, however, are only 0.4 percent of the entire API at issue, which consists of 2.86 million total lines." The 0.4% copy is considered to be small.
4) The effect of the use upon the potential market for or value of the copyrighted work: "Google’s new smartphone platform is not a market substitute for Java SE", and "Java SE’s copyright holder would benefit from the reimplementation of its interface into a different market".
Final thoughts: As the writter eloquently put it, "Google copied these lines not because of their creativity or beauty but because they would allow programmers to bring their skills to a new smartphone computing environment", and "enforcing the copyright on these facts risks causing creativity-related harms to the public". We still don't have a concrete definiton of "fair use" in practice, but at least in this case we see that it favors creativity and aims to avoid conflict of interest.