It's been years since I took Torts in law school but here is what I do remember:
1) It is almost a certainty that Google had an indemnification clause in their Android license. At face value, this would shield them from liability.
2) However, sort of like the waiver of liability you see on the back of your parking garage stub, many times these waivers are not worth more than the paper they are written on.
3) If Google knowingly and recklessly stole IP and passed it on to a third party claiming that it was it's own, I think there is still potential for liability. Especially when considering that these third parties relied on Android for their own products and will now suffer a material economic harm if the court sides against Google. Additionally, even though Google gave the software away for free, it is still making money off of these Android users. If I were Samsung or some other company that relied on Android, my claim would be that had Google disclosed that it does not own the rights to all the technology embedded in its product, I would have used a different operating system or never would have agreed to license it in the first place.
Here is a real world example: Suppose I lend you my car, and you get into an accident. In that scenario, you would typically assume responsibility for any damages. However, if I lend you my car and fail to reveal that the brakes do not work, and you get into an accident, the liability could be passed back to me. Now, let's take it a step further: imagine that I stole a car, lent it to you, and you got into an accident because the brakes were not working. I would not be absolved from liability in that situation because had I told you the car was stolen, would you have agreed to borrow it?
The key here is whether Google knew in advance that it was using "stolen" technology and passing it off as its own. This is why the Post It Notes are valuable evidence, even if they do not directly prove anything. Nevertheless, while there is a chance that Google might not be liable, if the court sides with MaxSound and third parties start getting licensing demands, I would expect more than one lawsuit against Google as a result. And for what it's worth, the cheaper, simpler solution may just be for Google to purchase the rights from MaxSound outright. Not to mention that if Google relies on third parties to license its software, it will be a PR nightmare for Google execs to try to mend those bridges once MaxSound starts sending out licensing demands.