It's muddled due to the peculiar nature of the appeals path in this case. In a normal copyright case, filed in a court in San Francisco as this case was, here is how things work.
1. A trial is held in a Federal district court. That court looks to the Federal copyright statue (17 USC), the Supreme Court, and the United States Court of Appeals for the Ninth Circuit (which I will just call 9th Circuit CoA from now on) for the copyright law that the court must follow.
2. If there are any copyright issues that the court cannot resolve using the sources mentioned above, it might also look to decisions of the Courts of Appeals for circuits other than the 9th Circuit, or to academic writings, or actually to anything else that might provide some insight.
None of these other sources are binding, though. Only the Supreme Court and the 9th Circuit CoA decisions are binding on a San Francisco Federal district court.
3. The district court reaches a decision, and the losing party appeals. The appeal goes to the 9th Circuit CoA. The 9th Circuit CoA makes a decision.
4. The 9th Circuit COA decision is binding precedent on all future copyright cases heard in district courts in the 9th Circuit.
Now compare this to a patent case. Assume it is purely a patent case. As with our hypothetical copyright case, let's assume this patent case is filed in a San Francisco Federal court.
Everything is the same as it is with the copyright case except replace "Court of Appeals for the Ninth Circuit" with "United States Court of Appeals for the Federal Circuit" (CAFC) [1]. Patent case appeals from district courts all go to CAFC regardless of which Circuit the district court is in.
Where it gets muddled is when a case is both a patent case and a copyright case. That was the case in Oracle vs. Google.
In that situation, the appeal from the district court goes to CAFC, and CAFC rules on both the patent aspects of the appeal and the copyright aspects. However, on the copyright aspects CAFC is supposed to follow the precedents of the appeals court for the Circuit, so in this case they are supposed to follow 9th Circuit CoA copyright precedent...and many legal scholars think they botched this.
This is a pretty messed up design because it creates a situation where you have one court (CAFC) interpreting another court's binding precedent (9th Circuit CoA), but there is no path to appeal the decision from the first court to the second court. In every other situation that comes to mind, if one court is supposed to follow the precedent of another court there is a way to have that second court review the first court.
CAFC's copyright ruling is binding on the district court in this particular case. It is not binding anywhere else. If, say, Apple and Microsoft got into a tussle over APIs and one sued the other in a district court in the 9th Circuit, that court would still look to what the 9th Circuit CoA has said, not to what CAFC says. CAFC would be just another non-Supreme Court, non-9th Circuit CoA source that the court could consider for insight but is not obligated to follow.
So, as long as an API dispute does not also involve patents, the legal status of APIs should be what it was before Oracle vs. Google.
That's assuming that you also think that if you end up getting sued it will not involve patents. If it involves patents, and your lawsuit is in the 9th, then you should assume that CAFC will rule consistently with their Oracle ruling at least until an API case makes it to the 9th Circuit CoA and they say something that makes it clear CAFC misunderstood 9th precedent.
[1] replace might not be quite correct. The district court in a patent case will look to the Supreme Court and CAFC for precedent, but it might also still look to the appeals court for its Circuit, too, because that court will have heard patent appeals before CAFC was created and some of those might still be precedent in that Circuit.