Having an open codec doesn't prevent at all using DRM.

And on a related note, Google's visions come to light quite clearly if you look at what they're focusing on: cloud computing, ultra-high speed connections. They don't want users to have any local storage. They just want to serve ads on all media. Very obvious of course, but it's interesting to see the grand scheme coming together.

Google doesn't want to kill mozilla. Open standards are good for the web and therefor good for Google. Google explicitly said that they want other browsers to copy the features of chrome because great broswers mean a better web experience for everyone which is good for google. A competitor such as mozilla that embraces open standard is actually a good thing for google, that's the kind of browser competitor they want, not IE.

As for freeing On2 codec, google made it clear on their press release when they bought on2 that having an open video standard was primordial for the web. And again, it's in their interest to make the web the best platform possible, and having a free and open video codec usable by all is a huge part of achieving that goal.

Letting the On2 codec locked in a drawer would be a huge mistake, it would help mpeg4 be the ubiquitous standard making any alternative irrelevant and useless (like vorbis or aac were with mp3, even though vorbis and aac were actually better). If there is any time to make use of On2, it's now and that's by making it open source.