I can't answer your question, because I don't know the answer.
However, I would recommend against relying on wereHamster's apparent mis-information... unless Google's policies are different in the jurisdiction that wereHamster is familiar with, in which case I apologize.
This is false. Source: I am a Googler who has released open source code, written in my own time, using my own hardware/software.
Here's how it works (in California, anyway):
Google reserves the right to review open source projects to determine whether there is overlap with a current or potential Google business. This is done by submitting a form that describes one's project and then waiting a while for a decision. If the decision is "yes", then you are free to work on your project with your own time/resources, and publish it under your own copyright.
Google being Google, almost anything could be construed as overlapping with Google business interests. However, my anecdata suggests that Google is quite liberal in this regard: I had no problems myself, and know a few others who also had no problems.
In this case (i.e. this Hacker News story), I'm guessing that we're talking about something different. I suspect that the project in question was written using Google time and resources, and it is IMO appropriate for Google to own the copyright.
However, I would recommend against relying on wereHamster's apparent mis-information... unless Google's policies are different in the jurisdiction that wereHamster is familiar with, in which case I apologize.