Google insofar doesn't seem interested in releasing Goobuntu publicly:
A post on the Register, claiming that Google might be close to rolling out a "Goobuntu" Linux desktop distro, has been making the usual rounds in the tech news circuit today. Despite today being earnings release day, presumably a very busy time at the Google press relations office, technology spokeswoman Sonya Borälv responded very quickly to my query on the topic. She said that "[w]e use Ubuntu internally but have no plans to distribute it outside of the company."
Mark Shuttleworth, Canonical Ltd.'s founder, also notes:
I keep getting asked about Google’s “distribution of Ubuntu”, so perhaps this is a good place for me to say that as far as I’m aware there is absolutely no truth to the rumour that Google plans to distribute a derivative of Ubuntu as a Google OS. As exciting as that may be for Linux, it wouldn’t make sense for Google, and so far they’ve been pretty sensible about their projects.
Google uses lots of Linux internally, I imagine they also have their own versions of Red Hat, SUSE, Debian, perhaps even Gentoo and of course Ubuntu. So don’t read too much into their use of Ubuntu – it’s just part of the picture, and nothing to get overly excited about. The “goobuntu” you may have heard of is just a modified version of Ubuntu. Technically, there’s likely to be a “goobian” and a “goohat” too . The good news is that the guys there have been good about sending us patches, and we do our best to integrate them into mainstream Ubuntu and push them on to Debian and upstream.
Thomas Bushnell, the tech lead of Google's Goobuntu team recently (August 29, 2012) discussed Goobuntu in his Ubuntu GNU/Linux at Google talk at LinuxCon, explaining that:
Bushnell explained that “Goobuntu is simply a light skin over standard Ubuntu.” In particular, Google uses the latest long term support (LTS) of Ubuntu. That means that if you download a copy of the latest version of Ubuntu, 12.04.1, you will, for most practical purposes, be running Goobuntu.
Google uses the LTS versions because the two-years between releases is much more workable than the every six-month cycle of ordinary Ubuntu releases. Besides, Google also tries to update and replace its hardware every two-years so that syncs nicely as well.
...without mentioning any plans to release Goobuntu publicly. Furthermore Bushnell mentions that Goobuntu uses proprietary software:
On top of this, Google has very strict security requirements. As Bushnell observes, “Google is a target Everyone wants to hack us.” So some programs that are part of the Ubuntu distribution are banned as potential security risks. These include any program “that calls home” to an outside server. On top of that Google uses its own proprietary in-house user PC network authentication that Bushnell says is “pushing the state of the art in network authentication, because we're such a high profile security target.”
That's possibly one of the reasons Google doesn't really seem interested in releasing Goobuntu publicly, at least anytime soon.