The XDA Developers Forum have figured out how to gain full access to the G1's code and jailbreak it entirely. Like the iPhone before it, the G1 is not easy to jailbreak but if you just follow some simple instructions then everything will be merry.

Once you have jailbroken the device you will then gain full access and the ability to read and write to the OS. You would have thought with Android open nature such devious acts was is not required, sadly it is.

ModMy Gphone

Here are the simple instructions you need to follow, if you are running Linux like I then this will not work:

Turn on WiFi in the G1 (Settings > Wireless Controls > Wi-Fi). Make sure you're connected to a network.

Start up PTerminal (search in the Market) and you'll get a prompt once its launched.

Enter cd system and hit Enter.

Enter cd bin and hit Enter.

Enter telnetd and hit Enter. You've now started telnet on your G1.

Enter netstat and hit Enter. You'll now see your G1's IP address. You can also find this in the Settings > Wireless Controls > Wi-Fi > and click on your network you're connected to. It will show you your IP.

Start up Terminal on your OS X machine, or bring up a command prompt on your Windows box. Type telnet [your.ip.address.we.just.found] and hit Enter/Return. So, if your IP was 192.168.1.101, you'd type telnet 192.168.1.101 and hit Enter/Return.

You are logged in as root now. To remount the system file as read write, type mount -oremount,rw /dev/block/mtdblock3 /system from the Terminal/Command Prompt and hit Enter/Return

There you have it, a jailbroken G1.