This says they are[1]: Interoperability has been succesfully used as a fair-use defense in the past, and commercial use decreases the chances of a fair-use ruling. Both points (interoperability and commercial use) are central to the Oracle v. Google case, and have been brought up by both sides. See here[2]:

I reached out to Collard, a partner at Dorsey & Whitney, who specializes in intellectual property... "In my opinion, the biggest problem for Google is the commercial nature of its use [of the APIs]," he said. "That is generally a strike against finding fair use. Its best argument is probably interoperability -- in other words, it should be fair use because Google must use the APIs in order to make its products interoperable."

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

[2]: https://adtmag.com/blogs/watersworks/2015/07/google-java-api...