According to the agreement, they have a grace period until Oct 30, but apparently they already published some source code.
Unfortunately it's still incomplete to some degree, but I'm looking forward to getting this sorted out.
Also, this source is not enough in order to run your own kernel on the TomTom GO, you will need some information on the firmware image layout and a particular blowfish key. For more details on the internals of the TomTom GO, please see the OpenTom of Christian Daniel.
I'm looking forward to convert to TomTom into a all-in-one car computer, including wardriving (USB WLAN with kismet) support and MP3/Ogg-Player with USB hard drive :) Not to forget bluetooth keyboard support, etc. :)