I suggest reading the Fortune article: Let Oracle Own APIs, Justice Dept Tells Top Court in Surprise Filing and DOJ's filing.
The DOJ filing which is worth reading encourages the US Supreme Court to deny Google's petition to hear its arguments to deny copyright protection to Oracle's Java related application programming interfaces (APIs).
It does a good job of explaining the scope of copyright protection for software:
Petitioner (Google) contends, however, that even if the declaring code is an “original work of authorship” under Section 102(a), it is not entitled to copyright protection because it constitutes a “method of operation” or “system” within the meaning of Section 102(b). That argument is incorrect. . . . Section 102(b) is not a limitation on what kinds of expressive works may be protected by a copyright. Rather, it is a limitation on how broadly the copyright extends.
DOJ stated, among other things, in the filing: "The Android platform uses the Java programming language, but [Google] purposely designed Android not to be compatible with the Java platform or interoperable with Java programs."
Google's response: "We still look forward to defending the concepts of interoperability that have traditionally contributed to innovation in the software industry."
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