A lot of the discussion in this thread is about what this sort of ruling means for people making compatible implementations of other people's APIs -- Unix, the PC BIOS, etc. But that's not what Google was intending to do here, they were using part of Oracle's Java tech to build their own, incompatible application format.

They're using Java "The Good Parts", the subset of Java that is platform neutral that most people use. By the time Android was launched, Java on the Desktop was already dead. Practically zero people write Java desktop apps not care about compatibility with them, the vast majority of Java code prior to Android lived in the cloud.

What makes Java valuable to most developers is byte-code portability, the widespread use of the language, the core APIs (not the GUI), and the developer tool chain.

The Sun licenses for Java go back to a time when they had a dream to displace Windows on the Desktop with all native desktop apps written in Java. That reality was delusional, but Java succeeded brilliantly on the server.

I don't know why you think this is relevant to the sort of precedent this sets legally. Oracle claims it is suing Google for making a deliberately incompatible set of libraries using their copyrighted material. The fact that Google's use of the APIs is deliberately incompatible is means that a ruling against Google is not necessarily a precedent that can be used against others who attempt to build compatible clean-room implementations of other systems, and that's just as true if you think that Google's lack of compatibility with Java SE was a good technical decision.

Most clones are incompatible in some way. WINE is not100% compatible with Windows, Linux is not compatible with AT&T Unix (ever looked at "cross platform" Unix source?)

My personal opinion is not about what is legal, but what I think is ethical and justified. The current system is broken and needs to be reformed.

You seem to want to defend the status quo. That's your prerogative, I think you're advocating for a world that makes everyone worse off, but we can agree to disagree.

Well, let's talk about WINE for a second. What I said wasn't "incompatible," it was "deliberately incompatible." WINE attempts to duplicate the Win32 APIs as they are implemented in various versions of Microsoft Windows. The entire point of WINE is to be interoperable, in order to allow programs that run on Windows to also run elsewhere. WINE may sometimes fail at this (man's reach must ever exceed his grasp, else what's a heaven for?), but it is certainly TRYING to be compatible. By the same token, the reason that Linux implements various APIs present in UNIX is so that it is compatible with software written for UNIX (or more accurately, to make software more portable between various types of UNIX and various types of Linux).

Google's use of the Java APIs is different; Google intentionally makes it so that Java applications do not run on Android and Android applications do not run on Sun's JVM. Google is not trying to implement those APIs for the purpose of interoperability. A finding that Google's appropriation of those APIs for their own runtime environment is not fair use is not a finding that WINE's use of Windows APIs in order to enable interoperability is not fair use. What's at stake here is more narrow than what several posters have surmised. You can argue that what's at stake here is still important, which is a discussion worth having, but posts in this thread about (for instance) how the PC compatible market wouldn't be allowed to exist under this ruling are mistaken.

Does the law make a distinction between copyright infringement based on unintentional incompatibility vs intentional incompatibility? I don't see it.

And why would it not be copyright infringement to implement a full API, but is copyright infringement to implement a subset of one?

When Phoenix cloned the PC bios, they did it on the assumption that if they reverse engineered the complete API specification, and then had a separate group of engineers perform the implementation, there would be no infringement, because no one in the history of computer science thought API interfaces could be copyrightable.

IBM was powerless to stop them, and clones flourished. With this precedent, would Phoenix have attempted the clone? Would IBM have not sued over copyright infringement of their interface?

Pretty much all clean room implementations since then have proceeded on the basis that implementing someone else's API, even against their wishes, is not an infringement. It's been the default assumption for decades.

To act like this Court decision has not flipped over decades of practice is putting way too much trust in the companies out there to show restraint and not unleash a tidal wave of copyright suits.

I don't think the deliberate making of Android incompatible with Java had much bearing in this case. Oracle might not have liked it, but it wasn't part of their claims, I don't think. It was discussed as part of the context for Google's choices.