First, we should separate the motivation for the lawsuit from the legal arguments. Corporations don't go to court to win legal arguments; they go to court to defend or promote their business.

I) The motivation for the lawsuit was that at the time, Java's main revenue stream was licensing Java IP (either an actual implementation or the permission to implement the spec) for use in mobile devices. That was how Sun made money off of Java. Java's commercial license allowed people to freely implement the specification as long as they pass the compatibility test, unless the implementation was for use in mobile devices -- this required a paid license. Google then created an implementation of (a part of) the spec, and didn't reach a licensing agreement with Sun (they couldn't agree on a price; I think Sun wanted $25M for the first five years or something). Google used Java IP to directly attack said IP's main revenue source. That is not to say that what they did wasn't legal, but that is why what they did mattered to Sun (and then Oracle) enough to sue them. Google needed Java because developing a language ecosystem suitable for phone application takes years. Google knew that such a lawsuit is forthcoming -- you can't come at a company like that and not expect one -- but hoped that they could defend their actions in court, at least on legal grounds. So that's what the lawsuit was about.

II) Now for the legal case. Oracle wanted to get their (in their view -- fair) share of Android no matter how, so they used -- as anyone does -- any legal argument they could think of which would get the desired business result, from patents to copyright. Some stuck, some didn't. In the end, it was the API copyright argument that convinced the (appeals) court. But before I say a few words about that, let me reiterate: Oracle didn't set out to copyright APIs; they set out to get a share of Android, which attacked their main Java revenue stream directly using their own IP. Anyway, Google claimed that APIs aren't copyrightable, but Oracle won that round. Now, I will not go into this question itself -- there are good arguments for both sides -- but only into its ramifications. Google started a massive PR campaign to convince people that that ruling is disastrous for them, but it isn't, and for several reasons.

First, it applies only to language-level APIs; not REST protocols, recently also referred to as APIs. This is not open to interpretation. Web "APIs" are not copyrightable for completely other reasons, reasons which are impossible (as much as anything in law is impossible) to argue against. Second, the court ruled that some of Google's argument regarding the copyrightability of APIs are really fair use arguments, and this is the second crucial point: if something is copyrighted, that does not mean you may not freely use it for some purposes. When it comes to interfaces, one fair use defense has been interoperability[1]. Courts have ruled it legal to "violate" copyright for the purpose of creating components that are interoperable with the original. This means that if you implement an API in order to break vendor lockin, you're probably within your right to do so. However, that is not what Google did in this particular case (Android is not interoperable with Java, only very, very partially). So while Google may still lose the fair-use question (which is still on the table), nearly all other implementors would still be protected by fair use.

To sum up the legal issue, while it has been in Google's best interest to cause panic, the ruling does not apply to any other player but Google because:

1. It only applies to language-level APIs; it does not and cannot apply to web APIs and other protocols (either software or hardware).

2. Implementing an API is protected by the interoperability fair-use defense, even if Google's particular (and highly unusual) use isn't.

And in any case, unless you use a company's (language-level) API against it, there is little chance they'll come after you; if you do, well, you knew they'd come after you even before this court case.

III) Finally, it is important to note that all along Google had the option of freely using OpenJDK. The use of OpenJDK does not require conformance with the Java standard; it is completely unencumbered. The reason Google opted not to do it was because at the time they were afraid phone manufacturers would not like OpenJDKs license, GPLv2 + the classpath exception, even though Android also make use of Linux, which is also licensed under the GPL. This reasoning seems to have changed now.

[1]: https://www.cs.duke.edu/courses/cps182s/fall02/cscopyright/C...