Whether usage is commercial or not is a big part of the first factor in the fair use test: https://en.wikipedia.org/wiki/Fair_use#1._Purpose_and_charac...

You could arguably implement Java without a license from Oracle provided you were using the GPL, as OpenJDK is released under the JDK, and presumably includes the entire Java API. The problem for Google, of course, is OEMs would've balked at being forced to open source all of their proprietary modifications to Android.

Wikipedia says the OpenJDK was released in 2007, so Google could've legally used the Java API under GPL terms, but chose not to, and also chose not to pay for Java licensing.

> > And things like something being non-commercial, such as a lot of open source software, is a major factor in determining whether or not usage is fair.

> Why it should?

Because its explicitly a factor, in the statute, for fair use analysis.

> It would mean that implementing commercial Java runtime without Oracle license is not possible?

Maybe, maybe not. If Google loses on both copyrightability and fair use, the entire case law on API fair use will be one negative instance. We might also get a more specific test articulated in the ruling, but we have no idea what that test would be now, so its hard to speculate (well, easy to speculate, but hard to judge which speculation is more accurate) what the impact would be on any other use.