I don't get one thing. I thought Java is supposedly open-source? How come there's proprietary source code? Or are these files part of a particular Java library developed by Sun that are not part of the Java that they open-sourced?
Basically you can't do shit if it isn't explicitly allowed.
As for could the just pay Oracle to license the code - they could have done at the time had Oracle, or Sun as it would have been at the time, agreed but they didn't. It would seem highly unlikely given that Oracle are currently suing them that they'd be willing to enter into such a license with Google now.
My guess is that the only out they'd have with this is if the purchase contract specified that any legal liability might remain with the previous owners but it's unusual to find anyone who will agree to that with a sale.
The possibilities are that they did not perform proper due diligence on the code that they bought, which should have brought this to light (and a giant the size of google really should know how to do a code audit) (bad), the second possibility is that they did do proper due diligence, were aware of the provenance of this chunk of code and chose to ignore it (bad), the third is that the code got incorporated after the sale (bad).
There are no 'goods' here, the central question is if this is a part that is critical.
That said, I'm fairly sure that any large enough software project that has had contributions from large numbers of sources is subject to this kind of pollution, unless very strict measures are taken to avoid it.
Not entirely; it might make a difference in how hard it is for Oracle to prove willful infringement (which increases the damages.
And even if it's irrelevant to the case, it's still an interesting question.
Google inherit everything the previous developer did including the intent or otherwise. It doesn't get to say "but we didn't know when we bought it", that's what due diligence and contacts are for.
(b) The longer ago it happened, the more likely it is that any evidence of how it happened has been lost. If so, even if it was willful, Oracle might have trouble proving it.