The bits where they emphasise that the copying was "transformative" as part of the "Purpose and Character of the Use" analysis are interesting:
« Google’s limited copying of the API is a transformative use. Google copied only what was needed to allow programmers to work in a different computing environment without discarding a portion of a familiar programming language. Google’s purpose was to create a different task-related system for a different computing environment (smartphones) and to create a platform — the Android platform — that would help achieve and popularize that objective. »
« Here Google’s use of the Sun Java API seeks to create new products. It seeks to expand the use and usefulness of Android-based smartphones. Its new product offers programmers a highly creative and innovative tool for a smartphone environment. To the extent that Google used parts of the Sun Java API to create a new platform that could be readily used by programmers, its use was consistent with that creative “progress” that is the basic constitutional objective of copyright itself. »
This suggests to me that someone who copies a set of function declarations for the purposes of, say, creating a free-software clone of an existing product might not be able to rely on this decision.
> This suggests to me that someone who copies a set of function declarations for the purposes of, say, creating a free-software clone of an existing product might not be able to rely on this decision.
They wouldn't need to rely on this decision.
The courts tend to frown on using IP law as a weapon against interoperability or legitimate competition outside the scope of what the IP law covers. If you get sued for copying Yoyodyne's API in order to develop an otherwise original piece of software whose purpose is to interact with other software that expects Yoyodyne's program, the appeals court is likely to smack the suit down citing Sega v. Accolade and Sony v. Connectix, and the SCOTUS (assuming it gets that far) is likely to agree.
One of Oracle's major arguments was that Android was not interoperable with regular Java, and in Oracle's position the fact that Google copied Java's declaring code just to screw Oracle over put Android outside the bounds of interoperability fair-use protection.
« Google’s limited copying of the API is a transformative use. Google copied only what was needed to allow programmers to work in a different computing environment without discarding a portion of a familiar programming language. Google’s purpose was to create a different task-related system for a different computing environment (smartphones) and to create a platform — the Android platform — that would help achieve and popularize that objective. »
« Here Google’s use of the Sun Java API seeks to create new products. It seeks to expand the use and usefulness of Android-based smartphones. Its new product offers programmers a highly creative and innovative tool for a smartphone environment. To the extent that Google used parts of the Sun Java API to create a new platform that could be readily used by programmers, its use was consistent with that creative “progress” that is the basic constitutional objective of copyright itself. »
This suggests to me that someone who copies a set of function declarations for the purposes of, say, creating a free-software clone of an existing product might not be able to rely on this decision.