Google isn't making a cellphone, they're making a platform.

First models expected in the second half of 2008.
http://googleblog.blogspot.com/2007/11/wheres-my-gphone.html

The platform is called Android.

"It is built to be truly open."
"Android is built on the open Linux Kernel."
http://www.openhandsetalliance.com/android_overview.html