Apache resigns from the Java Community Process executive committee

It's a bit more subtle than that. Just about any software that you distribute would carry an implicit patent license (at least in the US) for patents you owned. The GPL goes a step further and says that the patent license must be non-discriminatory to future downstreams which basically is anything that can claim to be a derivative product.

So in theory, even if I just copied a few lines of code from OpenJDK and implemented everything else from scratch, I still get full patent licenses. The catch is, if I copy anything from a GPL software, my license must be GPL-compatible and the end-result is something that is effectively GPL'd.

By the virtue of being Apache Licensed, there is no way Harmony can claim to be a derivative product of OpenJDK which means it doesn't get to share the patent license. If they integrated two lines of OpenJDK code and relicensed to GPL, they'd be covered.